Intel 845 Chipset: 82845 Memory Controller Hub (MCH) for SDR

Intel 845 Chipset: 82845 Memory Controller Hub (MCH) for SDR
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Intel® 845 Chipset: 82845
Memory Controller Hub (MCH)
for SDR
Datasheet
January 2002
Document Number: 290725-002
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®
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future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to them.
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Current characterized errata are available on request.
Contact your local Intel sales office or your distributor to obtain the latest specifications and before placing your product order.
2
2
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Copyright © 2001–2002, Intel Corporation
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Intel 82845 MCH for SDR Datasheet
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Contents
1
Introduction ........................................................................................................................11
1.1
1.2
1.3
1.4
2
Terminology and Notations ...................................................................................11
Reference Documents ..........................................................................................13
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Intel 845 Chipset System Architecture ................................................................14
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Intel 82845 MCH Overview .................................................................................14
1.4.1
System Bus Interface ............................................................................15
1.4.2
System Bus Error Checking ..................................................................15
1.4.3
System Memory Interface .....................................................................16
1.4.4
AGP Interface........................................................................................16
1.4.5
Hub Interface.........................................................................................17
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1.4.6
Intel MCH Clocking ..............................................................................17
1.4.7
System Interrupts ..................................................................................18
1.4.8
Powerdown Flow ...................................................................................18
Signal Description..............................................................................................................19
2.1
2.2
2.3
2.4
2.5
2.6
2.7
3
System Bus Signals ..............................................................................................21
SDR SDRAM Interface Signals.............................................................................23
Hub Interface Signals............................................................................................23
AGP Interface Signals...........................................................................................24
2.4.1
AGP Addressing Signals .......................................................................24
2.4.2
AGP Flow Control Signals .....................................................................25
2.4.3
AGP Status Signals ...............................................................................25
2.4.4
AGP Strobes Signals.............................................................................26
2.4.5
AGP/PCI Signals ...................................................................................26
Clocks, Reset, and Miscellaneous Signals ...........................................................28
Voltage Reference and Power Signals .................................................................29
Reset States During Reset ...................................................................................30
Register Description ..........................................................................................................31
3.1
3.2
3.3
3.4
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Register Terminology............................................................................................31
PCI Bus Configuration Space Access...................................................................32
3.2.1
Standard PCI Bus Configuration Mechanism........................................33
3.2.2
Routing Configuration Accesses ...........................................................33
I/O Mapped Registers ...........................................................................................34
3.3.1
CONF_ADDR—Configuration Address Register ..................................34
3.3.2
CONF_DATA—Configuration Data Register.........................................36
Memory-Mapped Register Space .........................................................................36
3.4.1
DRAMWIDTH—DRAM Width Register.................................................37
3.4.2
DQCMDSTR—Strength Control Register (SDQ and CMD
Signal Groups) ......................................................................................38
3.4.3
CKESTR—Strength Control Register (SCKE Signal Group) ................39
3.4.4
CSBSTR—Strength Control Register (SCS# Signal Group).................40
3.4.5
CKSTR—Strength Control Register (Clock Signal Group) ...................41
3.4.6
RCVENSTR—Strength Control Register (RCVENOUT
Signal Group) ........................................................................................42
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3.5
3.6
4
Host-Hub Interface Bridge Device Registers (Device 0)......................................43
3.5.1
VID—Vendor Identification Register (Device 0) ....................................45
3.5.2
DID—Device Identification Register (Device 0).....................................45
3.5.3
PCICMD—PCI Command Register (Device 0) .....................................46
3.5.4
PCISTS—PCI Status Register (Device 0).............................................47
3.5.5
RID—Revision Identification Register (Device 0)..................................48
3.5.6
SUBC—Sub-Class Code Register (Device 0).......................................48
3.5.7
BCC—Base Class Code Register (Device 0)........................................48
3.5.8
MLT—Master Latency Timer Register (Device 0) .................................49
3.5.9
HDR—Header Type Register (Device 0) ..............................................49
3.5.10 APBASE—Aperture Base Configuration Register (Device 0) ...............50
3.5.11 SVID—Subsystem Vendor Identification (Device 0) .............................51
3.5.12 SID—Subsystem Identification (Device 0) ............................................51
3.5.13 CAPPTR—Capabilities Pointer (Device 0) ............................................51
3.5.14 AGPM—AGP Miscellaneous Configuration Register (Device 0)...........52
3.5.15 DRB[0:7]—DRAM Row Boundary Registers (Device 0)........................52
3.5.16 DRA—DRAM Row Attribute Registers (Device 0) ................................53
3.5.17 DRT—DRAM Timing Register (Device 0) .............................................55
3.5.18 DRC—DRAM Controller Mode Register (Device 0) ..............................56
3.5.19 DERRSYN—DRAM Error Syndrome Register (Device 0) ....................58
3.5.20 EAP—Error Address Pointer Register (Device 0) .................................58
3.5.21 PAM[0:6]—Programmable Attribute Map Registers (Device 0) ...........59
3.5.22 FDHC—Fixed DRAM Hole Control Register (Device 0)........................62
3.5.23 SMRAM—System Management RAM Control Register (Device 0) ......63
3.5.24 ESMRAMC—Extended System Mgmt RAM Control
Register (Device 0)................................................................................64
3.5.25 ACAPID—AGP Capability Identifier Register (Device 0).......................65
3.5.26 AGPSTAT—AGP Status Register (Device 0) .......................................66
3.5.27 AGPCMD—AGP Command Register (Device 0)..................................67
3.5.28 AGPCTRL—AGP Control Register (Device 0)......................................68
3.5.29 APSIZE—Aperture Size (Device 0) .......................................................69
3.5.30 ATTBASE—Aperture Translation Table Base Register (Device 0).......70
3.5.31 AMTT—AGP Interface Multi-Transaction Timer Register (Device 0) ...71
3.5.32 LPTT—AGP Low Priority Transaction Timer Register (Device 0).........72
3.5.33 TOM—Top of Low Memory Register (Device 0) ...................................73
3.5.34 MCHCFG—MCH Configuration Register (Device 0).............................74
3.5.35 ERRSTS—Error Status Register (Device 0) .........................................75
3.5.36 ERRCMD—Error Command Register (Device 0) .................................76
3.5.37 SMICMD—SMI Command Register (Device 0) ....................................78
3.5.38 SCICMD—SCI Command Register (Device 0) .....................................78
3.5.39 SKPD—Scratchpad Data Register (Device 0) ......................................79
3.5.40 CAPID—Product Specific Capability Identifier Register (Device 0) ......79
Bridge Registers (Device 1) ..................................................................................80
3.6.1
VID1—Vendor Identification Register (Device 1) ..................................81
3.6.2
DID1—Device Identification Register (Device 1)...................................81
3.6.3
PCICMD1—PCI-PCI Command Register (Device 1)............................82
3.6.4
PCISTS1—PCI-PCI Status Register (Device 1)....................................83
3.6.5
RID1—Revision Identification Register (Device 1)................................84
3.6.6
SUBC1—Sub-Class Code Register (Device 1).....................................84
3.6.7
BCC1—Base Class Code Register (Device 1)......................................84
3.6.8
MLT1—Master Latency Timer Register (Device 1) ...............................85
3.6.9
HDR1—Header Type Register (Device 1) ............................................85
3.6.10 PBUSN1—Primary Bus Number Register (Device 1) ...........................85
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3.6.11
3.6.12
3.6.13
3.6.14
3.6.15
3.6.16
3.6.17
3.6.18
3.6.19
3.6.20
3.6.21
3.6.22
3.6.23
3.6.24
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SBUSN1—Secondary Bus Number Register (Device 1) ......................86
SUBUSN1—Subordinate Bus Number Register (Device 1)..................86
SMLT1—Secondary Master Latency Timer Register (Device 1) .........87
IOBASE1—I/O Base Address Register (Device 1) ...............................88
IOLIMIT1—I/O Limit Address Register (Device 1) ................................88
SSTS1—Secondary PCI-PCI Status Register (Device 1) .....................89
MBASE1—Memory Base Address Register (Device 1) ........................90
MLIMIT1—Memory Limit Address Register (Device 1) .........................90
PMBASE1—Prefetchable Memory Base Address
Register (Device 1)................................................................................91
PMLIMIT1—Prefetchable Memory Limit Address
Register (Device 1)................................................................................91
BCTRL1—PCI-PCI Bridge Control Register (Device 1) ........................92
ERRCMD1—Error Command Register (Device 1) ...............................93
DWTC—DRAM Write Thermal Management Control
Register (Device 1)................................................................................94
DRTC—DRAM Read Thermal Management Control
Register (Device 1)................................................................................95
System Address Map.........................................................................................................97
4.1
4.2
4.3
4.4
4.5
5
Memory Address Ranges .....................................................................................97
4.1.1
VGA and MDA Memory Space..............................................................99
4.1.2
PAM Memory Spaces..........................................................................100
4.1.3
ISA Hole Memory Space .....................................................................100
4.1.4
TSEG SMM Memory Space ................................................................101
4.1.5
IOAPIC Memory Space .......................................................................101
4.1.6
System Bus Interrupt APIC Memory Space ........................................101
4.1.7
High SMM Memory Space...................................................................101
4.1.8
AGP Aperture Space (Device 0 BAR) .................................................102
4.1.9
AGP Memory and Prefetchable Memory.............................................102
4.1.10 Hub Interface Subtractive Decode ......................................................102
AGP Memory Address Ranges...........................................................................102
4.2.1
AGP DRAM Graphics Aperture ...........................................................103
System Management Mode (SMM) Memory Range...........................................103
4.3.1
SMM Space Definition .........................................................................104
4.3.2
SMM Space Restrictions .....................................................................104
I/O Address Space..............................................................................................105
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Intel MCH Decode Rules and Cross-Bridge Address Mapping.........................105
4.5.1
Hub Interface Decode Rules ...............................................................105
4.5.2
AGP Interface Decode Rules ..............................................................106
Functional Description .....................................................................................................107
5.1
5.2
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System Bus .........................................................................................................107
5.1.1
Dynamic Bus Inversion........................................................................107
5.1.2
System Bus Interrupt Delivery .............................................................108
5.1.3
Upstream Interrupt Messages .............................................................108
System Memory Interface ...................................................................................109
5.2.1
Single Data Rate (SDR) SDRAM Interface Overview .........................109
5.2.2
Memory Organization and Configuration.............................................109
5.2.2.1
Configuration Mechanism For DIMMs ...............................110
5.2.3
Memory Address Translation and Decoding .......................................111
5.2.4
DRAM Performance Description .........................................................112
5.2.4.1
Data Integrity (ECC)...........................................................112
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5.3
5.4
5.5
5.6
6
Electrical Characteristics .................................................................................................119
6.1
6.2
6.3
6.4
7
Package Mechanical Information........................................................................134
Testability.........................................................................................................................137
8.1
8.2
6
Absolute Maximum Ratings ................................................................................119
Power Characteristics .........................................................................................119
Signal Groups .....................................................................................................120
DC Characteristics ..............................................................................................122
Ballout and Package Information.....................................................................................125
7.1
8
AGP Interface Overview .....................................................................................112
5.3.1
AGP Target Operations.......................................................................112
5.3.2
AGP Transaction Ordering ..................................................................114
5.3.3
AGP Signal Levels...............................................................................114
5.3.4
4x AGP Protocol..................................................................................114
5.3.5
Fast Writes ..........................................................................................114
5.3.6
AGP FRAME# Transactions on AGP ..................................................115
Power and Thermal Management ......................................................................117
5.4.1
Processor Power State Control ...........................................................117
5.4.2
Sleep State Control .............................................................................118
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Intel MCH Clocking ...........................................................................................118
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Intel MCH System Reset and Power Sequencing.............................................118
XOR Test Mode Initialization ..............................................................................137
XOR Chains ........................................................................................................138
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Figures
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Figure 1. Intel MCH Simplified Block Diagram.................................................................20
Figure 2. PAM Register Attributes .....................................................................................60
Figure 3. Addressable Memory Space ..............................................................................97
Figure 4. DOS Compatible Area Address Map..................................................................98
Figure 5. Extended Memory Range Address Map ............................................................98
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Figure 6. Intel 82845 MCH Ballout Diagram (Top View—Left Side) ..............................126
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Figure 7. Intel 82845 MCH Ballout Diagram (Top View—Right Side)............................127
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Figure 8. Intel MCH FC-BGA Package Dimensions (Top and Side View).....................134
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Figure 9. Intel MCH FC-BGA Package Dimensions (Bottom View)...............................135
Figure 10. XOR Tree Chain.............................................................................................137
Tables
Table 1. General Terminology ...........................................................................................11
Table 2. Data Type Notation..............................................................................................12
Table 3. Number Format Notation .....................................................................................12
Table 4. Memory Capacity.................................................................................................16
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Table 5. Intel MCH Clock Ratio Table .............................................................................17
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Table 6. Intel MCH Internal Device Assignments ............................................................32
Table 7. Memory-mapped Register Address Map.............................................................36
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Table 8. Intel MCH Configuration Space (Device 0) ........................................................43
Table 9. PAM Register Attributes ......................................................................................61
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Table 10. Intel MCH Configuration Space (Device 1) ......................................................80
Table 11. SMM Space Address Ranges .........................................................................104
Table 12. Supported DIMM Configurations .....................................................................109
Table 13. Data Bytes on DIMM Used for Programming DRAM Registers ......................110
Table 14. Address Translation and Decoding .................................................................111
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Table 15. AGP Commands Supported by the Intel MCH When Acting as
an AGP Target .................................................................................................113
Table 16. Data Rate Control Bits .....................................................................................115
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Table 17. PCI Commands Supported by the Intel MCH (When Acting
as a FRAME# Target) ......................................................................................115
Table 18. Absolute Maximum Ratings.............................................................................119
Table 19. Power Characteristics......................................................................................119
Table 20. Signal Groups ..................................................................................................120
Table 21. DC Characteristics...........................................................................................122
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Table 22. Intel 82845 MCH Ballout Listed Alphabetically by Signal Name ....................128
Table 23. XOR Chain 0 ...................................................................................................138
Table 24. XOR Chain 1 ...................................................................................................140
Table 25. XOR Chain 2 ...................................................................................................141
Table 26. XOR Chain 3 ...................................................................................................142
Table 27. XOR Chain 4 ...................................................................................................143
Table 28. XOR Chain 5 ...................................................................................................144
Table 29. XOR Chain 6 ...................................................................................................146
Table 30. XOR Chain 7 ...................................................................................................147
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Intel 82845 MCH for SDR Datasheet
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Revision History
Revision
Number
Description
Date
-001
Initial Release.
September 2001
-002
• Changed the document name to add the term “for SDR”.
January 2002
• DWTC—DRAM Write Thermal Management Control Register was
incorrectly placed in Device 0. It should be in Device 1.
• DRTC—DRAM Read Thermal Management Control Register was
incorrectly placed in Device 0. It should be in Device 1.
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Intel 82845 MCH for SDR Datasheet
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Intel® 82845 MCH Features
! Intel® Pentium® 4 Processor (478 pin package)
! Accelerated Graphics Port (AGP) Interface
!
!
!
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Support
 Enhanced Mode Scaleable Bus Protocol
 2x Address, 4x Data
 System Bus interrupt delivery
 400 MHz system bus
 System Bus Dynamic Bus Inversion (DBI)
 32-bit system bus addressing
 12 deep In-Order Queue
 AGTL+ bus driver technology with
integrated AGTL+ termination resistors
System Memory Support
 Directly supports one SDR SDRAM
channel, 64 bits wide (72 bits with ECC)
 133 MHz Single Data Rate (SDR) SDRAM
devices
 64 Mb, 128 Mb, 256 Mb and 512 Mb
technologies for x8 and x16 devices
 By using 64 Mb technology, the smallest
memory capacity possible is 32 MB
 Configurable optional ECC operation (single
bit Error Correction and multiple bit Error
Detection)
 Page sizes of 2 KB, 4 KB, 8 KB and 16 KB
(individually selected for every row)
 Thermal management
 Maximum of 3 Double-Sided DIMMs (6
rows populated) with unbuffered PC133
(with or without ECC)
Note: Mixed mode, populating ECC and
Non-ECC Memories simultaneously is not
supported.
 3 GB Maximum using 512 Mb technology
 Supports up to 24 simultaneous open pages
 Maximum memory bandwidth of 1.067 GB/s
with PC133
Hub Interface to Intel® 82801BA ICH2
 266 MB/s point-to-point hub interface to
ICH2
 66 MHz base clock
 MSI interrupt messages, power management
state change, SMI, SCI and SERR error
indication
Intel 82845 MCH for SDR Datasheet
!
!
 Supports a single AGP device (either a
connector or on the motherboard)
 Supports AGP 2.0 including 1x, 2x, and 4x
AGP data transfers and 2x/4x Fast Write
protocol
 Supports only 1.5 V AGP electrical
characteristics
 32 deep AGP request queue
 Delayed transaction support for AGP-toSystem Memory FRAME# semantic reads
System Interrupt Support
 System bus interrupt delivery mechanism
 Interrupts signaled as upstream memory
writes from AGP/PCI
 Supports peer MSI between hub interface
and AGP
 Provides redirection for IPI and upstream
interrupts to the system bus
Power Management
 SMRAM space remapping to A0000h
 Supports extended SMRAM space above
256 MB, additional TSEG from Top of
Memory
 SMRAM accesses from AGP or hub
interface are not supported
 PC ’99 suspend to DRAM support
 ACPI, Revision 1.0b compliant power
management
 APM, Revision 1.2 compliant power
management
 NT Hardware Design Guide, Version 1.0
compliant
Package
 MCH: 593 pin FC-BGA (37.5 x 37.5 mm)
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System Block Diagram
Intel ® Pentium ® 4
Processor
Intel ® 845 Chipset
System Memory
4x AGP
Graphics
Controller
AGP 2.0
Intel ® 82845
Memory
Controller Hub
(MCH)
SDRAM
Interface
SDRAM
Hub
Interface
2 IDE Drives
PCI
Slots
UltraATA/100
PCI Bus
4 USB Ports; 2 HC
AC '97 Codec(s)
(optional)
AC'97 2.1
PCI
Agent
Intel ® 82801BA
I/O Controller Hub
(ICH2)
LPC I/F
LAN Connect
Super I/O
Keyboard,
Mouse, FD, PP,
SP, IR
GPIO
FW H Flash
BIOS
sys_blk
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Intel 82845 MCH for SDR Datasheet
Introduction
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1
Introduction
The Intel® 82845 Memory Controller Hub (MCH) is designed for use with the Intel® Pentium® 4
processor in the 478-pin package. The Intel® 845 chipset contains two main components: the
82845 Memory Controller Hub (MCH) for the host bridge and the Intel 82801BA I/O Controller
Hub (ICH2) for the I/O subsystem. The MCH provides the processor interface, system memory
interface, AGP interface, and hub interface in an 845 chipset desktop platform.
This document describes the 82845 Memory Controller Hub (MCH) for use with SDR (Single
Data Rate) memory devices. Section 1.3 provides an overview of the 845 chipset.
1.1
Terminology and Notations
This section provides the definitions of some of the terms used in this document. Notations used
for data types and numbers are also included. In addition, Section 3.1 contains register
terminology definitions.
Table 1. General Terminology
Term
Description
MCH
The Memory Controller Hub component that contains the processor interface, System
Memory DRAM controller, and AGP interface. It communicates with the I/O controller
hub (ICH2) and other IO controller hubs over proprietary interconnect called the hub
interface.
ICH2
The I/O Controller Hub component that contains the primary PCI interface, LPC
interface, USB, ATA-100, AC ’97, and other I/O functions. It communicates with the
MCH over a proprietary interconnect called the hub interface.
Host
This term is used synonymously with processor.
Core
The internal base logic in the MCH.
System Bus
Processor-to-MCH interface. The system bus runs at 400 MHz, from a 100 MHz quadpumped clock. It consists of source synchronous transfers for address and data, and
system bus interrupt delivery.
Hub Interface
The proprietary hub interconnect that connects the MCH to the ICH2. In this document
hub interface cycles originating from or destined for the primary PCI interface on the
ICH2 are generally referred to as hub interface cycles.
Accelerated
Graphics Port
(AGP)
Refers to the AGP interface that is in the MCH. The MCH supports AGP 2.0 compliant
components only with 1.5 V signaling level. PIPE# and SBA addressing cycles and their
associated data phases are generally referred to as AGP transactions. FRAME# cycles
over the AGP bus are generally referred to as AGP/PCI transactions.
PCI_A
The physical PCI bus, driven directly by the ICH2 component. It supports 5 V, 32-bit,
33 MHz PCI 2.2 compliant components. Communication between PCI_A and the MCH
occurs over the hub interface.
Note: Even though this PCI bus is referred to as PCI_A, it is not PCI Bus #0 from a
configuration standpoint.
Full Reset
®
A full MCH reset is defined in this document when RSTIN# is asserted.
Intel 82845 MCH for SDR Datasheet
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Introduction
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Term
Description
GART
Graphics Aperture Re-map Table. This table contains the page re-map information used
during AGP aperture address translations.
GTLB
Graphics Translation Look-aside Buffer. A cache used to store frequently used GART
entries.
UP
Uni-Processor.
DBI
Dynamic Bus inversion.
MSI
Message Signaled Interrupts. MSIs allow a device to request interrupt service via a
standard memory write transaction instead of through a hardware signal.
IPI
Inter Processor Interrupt.
SDR
Single Data-Rate SDRAM memory.
Table 2. Data Type Notation
Data Type
Size
bit (b)
Smallest unit, 0 or 1
byte
8 bits
word
16 bits = 2 bytes
DWord (DW)
Doubleword: 32 bits = 4 bytes
QWord (QW)
Quadword: 8 bytes = 4 words
DQWord (DQW)
Double Quadword. 16 bytes or 8 words. This is sometimes
referred to as a Superword (SW or SWord), and is also
referred to as a “Cache Line”.
Kilobyte (KB)
1024 bytes
Megabit (Mb)
1, 048,576 bits = 128 KB
Megabyte (MB)
1,048,576 bytes = 1024 KB
Gigabit (Gb)
1024 Mb
Gigabyte (GB)
1024 MB
Table 3. Number Format Notation
Number Format
Notation
Decimal (default)
12
Example
14
Binary
b
1110b
Hex
h
0Eh
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Intel 82845 MCH for SDR Datasheet
Introduction
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1.2
Reference Documents
Document
Document Number
/ Location
Intel® Pentium 4 Processor in a 478 Pin Package and Intel® 845 Chipset Platform for
SDR Design Guide
298354
Intel® 82801BA I/O Controller Hub (ICH2) and Intel® 82801BAM I/O Controller Hub
(ICH2-M) Datasheet
290687
Intel® 845 Chipset Thermal and Mechanical Design Guidelines for SDR
298586
®
Intel 82802AB/AC Firmware Hub (FWH) Datasheet
290658
PCI Local Bus Specification, Revision 2.1
Contact Intel Field
Representative
Accelerated Graphics Port Interface Specification, Revision 2.0
www.agpforum.org
®
Intel Pentium 4 Processor Datasheet
PC SDRAM Specification, Rev. 1.7
developer.intel.com
Note: See the Intel® Pentium 4 Processor in a 478 Pin Package and Intel® 845 Chipset Platform Design
Guide for an expanded set of related documents.
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Intel 82845 MCH for SDR Datasheet
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Introduction
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1.3
Intel® 845 Chipset System Architecture
The MCH provides the processor interface, system memory interface, AGP interface, and hub
interface in an 845 chipset desktop platform. The processor interface supports the Pentium 4
processor subset of the Extended Mode of the Scalable Bus Protocol. The MCH supports a single
channel of PC133 SDRAM. The MCH contains advanced power management logic. The 845
chipset platform supports the I/O Controller Hub 2 (ICH2) to provide the features required by a
desktop platform.
®
Intel 82801BA I/O Controller Hub 2 (ICH2)
The ICH2 is a highly integrated multifunctional I/O Controller Hub that provides the interface to
the PCI Bus and integrates many of the functions needed in today’s PC platforms. The MCH and
ICH2 communicate over a dedicated hub interface. The 82801BA ICH2 Functions and capabilities
include:
• PCI Rev 2.2 compliant with support for 33 MHz PCI operations
• Supports up to 6 Request/Grant pairs (PCI slots)
• Power management logic support
• Enhanced DMA controller, interrupt controller, and timer functions
• Integrated IDE controller; Ultra ATA/100/66/33
• USB host interface; 2 host controllers and supports 4 USB ports
• Integrated LAN controller
• System Management Bus (SMBus) compatible with most I2C devices; ICH2 has both bus
master and slave capability
• AC ’97 2.1 compliant link for audio and telephony codecs; up to 6 channels (ICH2)
• Low Pin Count (LPC) interface
• FWH Interface (FWH Flash BIOS support)
• Alert on LAN* (AOL and AOL2)
1.4
Intel® 82845 MCH Overview
The MCH role in a system is to manage the flow of information between its four interfaces: the
system bus, the memory interface, the AGP port, and the hub interface. The MCH arbitrates
between the four interfaces, when each initiates an operation. While doing so, the MCH supports
data coherency via snooping and performs address translation for access to AGP Aperture
memory. To increase system performance, the MCH incorporates several queues and a write
cache.
The MCH is in a 593 pin FC-BGA package and contains the following functionality:
• Supports single Pentium 4 processor configuration at 400 MHz
• AGTL+ system bus with integrated termination supporting 32-bit system bus addressing
• Up to 3 GB (w/ 512 Mb technology) of PC133 SDRAM
• 1.5 V AGP interface with 4x SBA/data transfer and 2x/4x fast write capability
• 8 bit, 66 MHz 4x hub interface to the ICH2
• Distributed arbitration for highly concurrent operation
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Introduction
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1.4.1
System Bus Interface
The MCH is optimized for the Pentium 4 processor. The primary enhancements over the
Compatible Mode P6 bus protocol are:
• Source synchronous double-pumped address
• Source synchronous quad-pumped data
• System bus interrupt and side-band signal delivery
The MCH supports a 64-byte cache line size. Only one processor is supported at a system bus
frequency of 400 MHz. The MCH supports a 3:4 host-to-memory frequency ratio (using the
100 MHz clock). The MCH integrates AGTL+ termination resistors on all of the AGTL+ signals.
The MCH supports 32-bit system bus addresses, allowing the processor to access the entire 4 GB
of the MCH memory address space.
The MCH has a 12-deep In-Order Queue to support up to twelve outstanding pipelined address
requests on the system bus. The MCH supports two outstanding defer cycles at a time; however,
only one to any particular I/O interface. Processor-initiated I/O cycles are positively decoded to
AGP/PCI or MCH configuration space and subtractively decoded to the hub interface. Processorinitiated memory cycles are positively decoded to AGP/PCI or system memory, and are again
subtractively decoded to the hub interface, if under 4 GB. AGP semantic memory accesses
initiated from AGP/PCI to system memory are not snooped on the system bus. Memory accesses
initiated from AGP/PCI using PCI semantics and from the hub interface to system memory will be
snooped on the system bus. Memory accesses whose addresses lie within the AGP aperture are
translated using the AGP address translation table, regardless of the originating interface.
1.4.2
System Bus Error Checking
The MCH does not generate parity, nor check parity for data, address/request, and response
signals on the processor bus.
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Introduction
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1.4.3
System Memory Interface
The MCH directly supports one channel of PC133 SDRAM. The memory interface supports
Single Data Rate (SDR) devices with densities of 64 Mb, 128 Mb, 256 Mb, and 512 Mb
technology. The memory interface also supports variable page sizes of 2 KB, 4 KB, 8 KB, and
16 KB. Page size is individually selected for every row and a maximum of 8 pages per DIMM may
be opened simultaneously.
The MCH supports a maximum of 3 double-sided DIMMs (6 rows populated) with unbuffered
PC133 (with or without ECC) Note that in mixed mode, populating ECC and Non-ECC memories
simultaneously is not supported.
Table 4. Memory Capacity
Technology
SDR (PC133)
Maximum
64 Mb
384 MB
128 Mb
768 MB
256 Mb
1.5 GB
512 Mb
3 GB
The memory interface provides optional ECC error checking for system memory data integrity.
During system memory writes, ECC is generated on a QWord (64 bit) basis. Because the MCH
stores only entire cache lines in its internal buffers, partial QWord writes initially cause a read of
the underlying data, and their write-back into memory is no different from that of a complete cache
line. During system memory reads, and the read of the data that underlies partial writes, the MCH
supports detection of single-bit and multiple-bit errors, and will correct single-bit errors when
correction is enabled.
The MCH supports a thermal management scheme to selectively manage reads and/or writes.
Thermal management can be triggered by preset read/write bandwidth limits.
1.4.4
AGP Interface
A single AGP component or connector (not both) is supported by the MCH AGP interface. The
AGP buffers operate only in 1.5 V mode. They are not 3.3 V safe.
The AGP interface supports 1x/2x/4x AGP signaling and 2x/4x fast writes. AGP semantic cycles
to system memory are not snooped on the system bus. PCI semantic cycles to system memory are
snooped on the system bus. The MCH supports PIPE# or SBA[7:0] AGP address mechanisms, but
not both simultaneously. Either the PIPE# or the SBA[7:0] mechanism must be selected during
system initialization. Both upstream and downstream addressing is limited to 32 bits for AGP and
AGP/PCI transactions. The MCH contains a 32 deep AGP request queue. High-priority accesses
are supported. All accesses from the AGP/PCI interface that fall within the Graphics Aperture
address range pass through an address translation mechanism with a fully associative 20 entry
TLB. Accesses between AGP and hub interface are limited to memory writes originating from the
hub interface destined for AGP. The AGP interface is clocked from a dedicated 66 MHz clock
(66IN). The AGP-to-host/core interface is asynchronous.
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Introduction
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1.4.5
Hub Interface
The 8-bit hub interface connects the MCH to the ICH2. All communication between the MCH and
the ICH2 occurs over the hub interface. The hub interface runs at 66 MHz / 266 MB/s. In addition
to the normal traffic types, the following communication also occurs over the hub interface:
• Interrupt related messages
• Power management events as messages
• SMI, SCI, and SERR error indication messages
It is assumed that the hub interface is always connected to an ICH2.
1.4.6
Intel® MCH Clocking
The MCH has the following clock input pins:
• Differential BCLK for the host interface
• 66 MHz clock input for the AGP and hub interface
Clock synthesizer chip(s) generate the system host clocks, AGP and hub interface clocks, and PCI
clocks. The system bus target speed is 400 MHz. The MCH does not require any relationship
between the HCLKIN host clock and the 66 MHz clock generated for AGP and the hub interface;
they are asynchronous to each other. The AGP and hub interface runs at a constant 66 MHz base
frequency. The hub interface runs at 4x. AGP transfers can be 1x, 2x, or 4x. Table 5 indicates the
supported frequency ratios between the various interfaces.
®
Table 5. Intel MCH Clock Ratio Table
®
Interface
Speed
Processor BCLK
(100 MHz)
Memory
SDR 133 MHz
3:4 synchronous
AGP
66 MHz
Asynchronous
Hub interface
66 MHz
Asynchronous
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Introduction
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1.4.7
System Interrupts
The MCH supports both Intel 8259 and Pentium 4 processor interrupt delivery mechanisms. The
serial APIC interrupt mechanism is not supported.
Intel 8259 support consists of flushing inbound hub interface write buffers when an Interrupt
Acknowledge cycle is forwarded from the system bus to the hub interface.
The MCH supports the Pentium 4 processor interrupt delivery mechanism. IOxAPIC and PCI MSI
interrupts are generated as memory writes. The MCH decodes upstream memory writes to the
range 0FEE0_0000h–0FEEF_FFFFh from AGP and the hub interface as message-based interrupts.
The MCH forwards the memory writes, along with the associated write data, to the system bus as
an interrupt message transaction. Note that since this address does not decode as part of system
memory, the write cycle and the write data are not forwarded to system memory via the write
buffer. The MCH provides the response and TRDY# for all interrupt message cycles, including the
ones originating from the MCH. The MCH supports interrupt re-direction for inter-processor
interrupts (IPIs) as well as upstream interrupt memory writes.
For message-based interrupts, system write-buffer coherency is maintained by relying on strict
ordering of memory writes. The MCH ensures that all memory writes received from a given
interface prior to an interrupt message memory write are delivered to the system bus for snooping
in the same order that they occur on the given interface.
1.4.8
Powerdown Flow
Since the MCH is powered down during STR, the MCH cannot maintain any state information
when exiting STR. Thus, the entire initialization process when exiting STR must be performed by
the BIOS via accesses to the DRC2 register.
Entry into STR (ACPI S3) is initiated by the Operating System (OS), based on detecting a lack of
system activity. The OS unloads all system device drivers as part of the process of entering STR.
The OS then writes to the PM1_CNT I/O register in the ICH2 to trigger the transition into STR.
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Signal Description
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2
Signal Description
This chapter provides a detailed description of the MCH signals. The signal descriptions are
arranged in functional groups according to their associated interface (see Figure 1). The states of
all of the signals during reset are provided in the System Reset section.
The “#” symbol at the end of a signal name indicates that the active, or asserted state occurs when
the signal is at a low voltage level. When “#” is not present after the signal name the signal is
asserted when at the high voltage level.
The following notations are used to describe the signal type:
I
Input pin
O
Output pin
I/O
Bi-directional Input/Output pin
s/t/s
Sustained Three-state. This pin is driven to its inactive state prior to threestating.
as/t/s
Active Sustained Three-state. This applies to some of the hub interface signals.
This pin is weakly driven to its last driven value.
The signal description also includes the type of buffer used for the particular signal:
AGTL+
Open Drain AGTL+ interface signal. Refer to the AGTL+ I/O Specification for
complete details. The MCH integrates AGTL+ termination resistors.
AGP
AGP interface signals. These signals are compatible with AGP 2.0 1.5 V
Signaling Environment DC and AC Specifications. The buffers are not 3.3 V
tolerant.
CMOS
CMOS buffers.
Ref
Voltage reference signal
Note: System address and data bus signals are logically inverted signals. In other words, the actual
values are inverted of what appears on the system bus. This must be taken into account and the
addresses and data bus signals must be inverted inside the MCH. All processor control signals
follow normal convention. A “0” indicates an active level (low voltage) if the signal is followed by
“#” symbol, and a “1” indicates an active level (high voltage) if the signal has no “#” suffix.
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Intel 82845 MCH for SDR Datasheet
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Signal Description
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®
Figure 1. Intel MCH Simplified Block Diagram
HA[31:3]#
HD[63:0]#
ADS#
BNR#
BP RI#
DBSY#
DE FE R#
DRDY#
HIT#
HITM#
HLOCK#
HREQ[4:0]#
HTRDY#
RS[2:0]#
CPURS T#
BR0#
DBI[3:0]#
HADSTB[1:0]#
HDS TB P[3:0]/HDSTBN[3:0]
P rocessor
System
B us
Interface
SCS[11:0]#
SM A[12:0]
SBS[1:0]
SRAS#
SCAS#
SW E#
SDQ[63:0]
SCB[7:0]
SCKE[5:0]
RDCLKO
RDCLK IN
SDRAM
Interface
HI_[10:0]
HI_S TB , HI_STB#
Hub
Interface
SBA[7:0]
PIPE #
ST[2:0]
RBF#
WBF#
AD_STB[1:0], AD_STB [1:0]#
SBSTB, SBSTB#
AGPRCOM P
G_FRAM E#
G_IRDY#
G_TRDY#
G_S TO P#
G_DEV SEL#
G_REQ#
G_G NT#
G_A D[31:0]
G_C/BE [3:0]#
G_P AR
AGP
Interface
HVREF
SDREF
HI_REF
AGPREF
HLRCOM P
GRCOM P
HRCOM P[1:0]
HSW NG[1:0]
SMRCOM P
VCC1_5
VCC1_8
VCCSM
VCCA[1:0]
VTT
VSS
VSSA[1:0]
System
Mem ory
Voltage
Refernce,
PLL Power
BCLK, BCLK#
66IN
SCK[11:0]
RSTIN#
TESTIN#
Clocks
and
Reset
block_dia_845
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Intel 82845 MCH for SDR Datasheet
Signal Description
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2.1
System Bus Signals
Signal Name
Type
Description
ADS#
I/O
AGTL+
Address Strobe: The system bus owner asserts ADS# to indicate the first
of two cycles of a request phase.
BNR#
I/O
AGTL+
Block Next Request: BNR# is used to block the current request bus
owner from issuing a new request. This signal dynamically controls the
system bus pipeline depth.
BPRI#
O
AGTL+
Bus Priority Request: The MCH is the only Priority Agent on the system
bus. It asserts this signal to obtain the ownership of the address bus. This
signal has priority over symmetric bus requests and will cause the current
symmetric owner to stop issuing new transactions unless the HLOCK#
signal was asserted.
BR0#
I/O
AGTL+
Bus Request 0#: The MCH pulls the processor bus BR0# signal low
during CPURST#. The signal is sampled by the processor on the active-toinactive transition of CPURST#. The minimum setup time for this signal is
4 BCLKs. The minimum hold time is 2 BCLKs and the maximum hold time
is 20 BCLKs. BR0# should be three-stated after the hold time requirement
has been satisfied.
CPURST#
O
AGTL+
Processor Reset: The CPURST# pin is an output from the MCH. The
MCH asserts CPURST# while RSTIN# (PCIRST# from the ICH2) is
asserted and for approximately 1 ms after RSTIN# is deasserted. The
CPURST# allows the processor to begin execution in a known state.
DBSY#
I/O
AGTL+
Data Bus Busy: DBSY# is used by the data bus owner to hold the data
bus for transfers requiring more than one cycle.
DEFER#
O
AGTL+
Defer Response: This signal, when asserted, indicates that the MCH will
terminate the transaction currently being snooped with either a deferred
response or with a retry response.
DBI[3:0]#
I/O
AGTL+
Dynamic Bus Inversion: DBI[3:0]# are driven along with the HD[63:0]#
signals. DBI[3:0]# Indicate if the associated data signals are inverted.
DBI[3:0]# are asserted such that the number of data bits driven electrically
low (low voltage) within the corresponding 16-bit group never exceeds 8.
DBI[x]#
DBI3#
DBI2#
DBI1#
DBI0#
®
Data Bits
HD[63:48]#
HD[47:32]#
HD[31:16]#
HD[15:0]#
DRDY#
I/O
AGTL+
Data Ready: Asserted for each cycle that data is transferred.
HA[31:3]#
I/O
AGTL+
Host Address Bus: HA[31:3]# connect to the system address bus. During
processor cycles, HA[31:3]# are inputs. The MCH drives HA[31:3]# during
snoop cycles on behalf of the hub interface and AGP/Secondary PCI
initiators. HA[31:3]# are transferred at 2x rate. Note that the address is
inverted on the system bus.
HADSTB[1:0]#
I/O
AGTL+
Host Address Strobe: The source synchronous strobes used to transfer
HA[31:3]# and HREQ[4:0]# at the 2x transfer rate.
Intel 82845 MCH for SDR Datasheet
Strobe
Address Bits
HADSTB0#
HADSTB1#
HA[16:3]#, HREQ[4:0]#
HA[31:17]#
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Signal Description
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Signal Name
Type
Description
HD[63:0]#
I/O
AGTL+
Host Data: These signals are connected to the system data bus.
HD[63:0]# are transferred at a 4x rate. Note that the data signals are
inverted on the system bus.
HDSTBP[3:0]#
I/O
AGTL+
Differential Host Data Strobes: The differential source synchronous
strobes used to transfer HD[63:0]# and DBI[3:0]# at the 4x transfer rate.
HDSTBN[3:0]#
Strobe
Data Bits
HDSTBP3#, HDSTBN3#
HDSTBP2#, HDSTBN2#
HDSTBP1#, HDSTBN1#
HDSTBP0#, HDSTBN0#
HD[63:48]#, DBI3#
HD[47:32]#, DBI2#
HD[31:16]#, DBI1#
HD[15:0]#, DBI0#
HIT#
I/O
AGTL+
Hit: This signal indicates that a caching agent holds an unmodified version
of the requested line. HIT# is also driven in conjunction with HITM# by the
target to extend the snoop window.
HITM#
I/O
AGTL+
Hit Modified: This signal indicates that a caching agent holds a modified
version of the requested line and that this agent assumes responsibility for
providing the line. HITM# is also driven in conjunction with HIT# to extend
the snoop window.
HLOCK#
I
AGTL+
Host Lock: All system bus cycles sampled with the assertion of HLOCK#
and ADS#, until the negation of HLOCK# must be atomic (i.e., no hub
interface or AGP snoopable access to system memory are allowed when
HLOCK# is asserted by the processor).
HREQ[4:0]#
I/O
AGTL+
Host Request Command: These signals define the attributes of the
request. In Enhanced Mode HREQ[4:0]# are transferred at 2x rate.
HREQ[4:0]# are asserted by the requesting agent during both halves of
Request Phase. In the first half the signals define the transaction type to a
level of detail that is sufficient to begin a snoop request. In the second half
the signals carry additional information to define the complete transaction
type.
The transactions supported by the MCH host bridge are defined in the
Section 5.1.
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HTRDY#
O
AGTL+
Host Target Ready: HTRDY# indicates that the target of the processor
transaction is able to enter the data transfer phase.
RS[2:0]#
O
AGTL+
Response Status: RS[2:0]# indicates the type of response according to
the following the table:
RS[2:0]
Response Type
000
001
010
011
100
101
110
111
Idle state
Retry response
Deferred response
Reserved (not driven by MCH)
Hard Failure (not driven by MCH)
No data response
Implicit Write back
Normal data response
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Signal Description
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2.2
SDR SDRAM Interface Signals
Signal Name
SCS[11:0]#
Type
O
CMOS
Description
Chip Select: These signals select the particular SDRAM components
during the active state.
Note: There are two SCS# signals per SDRAM row. These signals can
be toggled on every rising system memory clock edge.
2.3
SMA[12:0]
O
CMOS
Multiplexed Memory Address: These signals are used to provide the
multiplexed row and column address to SDRAM.
SBS[1:0]
O
CMOS
Memory Bank Select: SBS[1:0] define the banks that are selected within
each SDRAM row. The SMA and SBS signals combine to address every
possible location in a SDRAM device.
SRAS#
O
CMOS
SDRAM Row Address Strobe: SRAS# is Used with SCAS# and SWE#
(along with SCS#) to define the DRAM commands.
SCAS#
O
CMOS
SDRAM Column Address Strobe: SCAS# is used with SRAS# and
SWE# (along with SCS#) to define the SDRAM commands.
SWE#
O
CMOS
Write Enable: SWE# is used with SCAS# and SRAS# (along with SCS#)
to define the SDRAM commands.
SDQ[63:0]
I/O
CMOS
Data Lines: These signals are used to interface to the SDRAM data bus.
SCB[7:0]
I/O
CMOS
Check Bit Data Lines: These signals are used to interface to the
SDRAM ECC signals.
SCKE[5:0]
O
CMOS
Clock Enable: These pins are used to signal a self-refresh or
Powerdown command to a SDRAM array when entering system
suspend. SCKE is also used to dynamically powerdown inactive SDRAM
rows. There is one SCKE per SDRAM row. These signals can be toggled
on every rising SCLK edge.
RDCLKO
O
CMOS
Clock Output: RDCLKO is used to emulate source-synch clocking for
reads. This signal connects to RDCLKIN.
RDCLKIN
I
CMOS
Clock Input: RDCLKIN is used to emulate source-synch clocking for
reads. This signal connects to RDCLKO.
Hub Interface Signals
Signal Name
®
Type
Description
HI_[10:0]
I/O
CMOS
Hub Interface Signals: Signals used for the hub interface.
HI_STB
I/O
CMOS
Hub Interface Strobe: One of two differential strobe signals used to
transmit or receive packet data over the hub interface.
HI_STB#
I/O
CMOS
Hub Interface Strobe Compliment: One of two differential strobe
signals used to transmit or receive packet data over the hub interface.
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Signal Description
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2.4
AGP Interface Signals
2.4.1
AGP Addressing Signals
Signal Name
PIPE#
Type
Description
I
AGP
Pipelined Read: This signal is asserted by the AGP master to indicate a
full-width address is to be enqueued on by the target using the AD bus.
One address is placed in the AGP request queue on each rising clock
edge while PIPE# is asserted. When PIPE# is deasserted, no new
requests are queued across the AD bus.
During SBA Operation: Not Used.
During FRAME# Operation: Not Used.
PIPE# is a sustained three-state signal from masters (graphics
controller), and is an MCH input.
Note: Initial AGP designs may not use PIPE# (i.e., PCI only 66 MHz).
Therefore, an 8 kΩ pull-up resistor connected to this pin is
required on the motherboard.
SBA[7:0]
I
AGP
Sideband Address: These signals are used by the AGP master
(graphics controller) to place addresses into the AGP request queue.
The SBA bus and AD bus operate independently. That is, a transaction
can proceed on the SBA bus and the AD bus simultaneously.
During PIPE# Operation: Not Used.
During FRAME# Operation: Not Used.
Note: When sideband addressing is disabled, these signals are
isolated (no external/internal pull-up resistors are required).
NOTE: The above table contains two mechanisms to queue requests by the AGP master. Note that the
master can only use one mechanism. The master may not switch methods without a full reset of the
system. When PIPE# is used to queue addresses the master is not allowed to queue addresses using
the SBA bus. For example, during configuration time, if the master indicates that it can use either
mechanism, the configuration software will indicate which mechanism the master will use. Once this
choice has been made, the master will continue to use the mechanism selected until the master is
reset (and reprogrammed) to use the other mode. This change of modes is not a dynamic mechanism
but rather a static decision when the device is first being configured after reset.
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Signal Description
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2.4.2
AGP Flow Control Signals
Signal Name
RBF#
Type
Description
I
AGP
Read Buffer Full: RBF# indicates if the master is ready to accept
previously requested low priority read data. When RBF# is asserted, the
MCH is not allowed to initiate the return low priority read data. That is, the
MCH can finish returning the data for the request currently being
serviced. RBF# is only sampled at the beginning of a cycle. If the AGP
master is always ready to accept return read data, then it is not required
to implement this signal.
During FRAME# Operation: Not Used.
WBF#
I
AGP
Write-Buffer Full: Indicates if the master is ready to accept fast write
data from the MCH. When WBF# is asserted, the MCH is not allowed to
drive fast write data to the AGP master. WBF# is only sampled at the
beginning of a cycle. If the AGP master is always ready to accept fast
write data, then it is not required to implement this signal.
During FRAME# Operation: Not Used.
2.4.3
AGP Status Signals
Signal Name
ST[2:0]
Type
O
AGP
Description
Status: ST[2:0] provides information from the arbiter to an AGP Master
on what it may do. ST[2:0] only have meaning to the master when its
G_GNT# is asserted. When G_GNT# is deasserted, these signals have
no meaning and must be ignored. Refer to the AGP Interface
Specification, Revision 2.0 for further explanation of the ST[2:0] values
and their meanings.
During FRAME# Operation: These signals are not used during
FRAME#-based operation, except that a ‘111’ indicates that the master
may begin a FRAME# transaction.
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Signal Description
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2.4.4
AGP Strobes Signals
Signal Name
2.4.5
Type
Description
AD_STB0
I/O
(s/t/s)
AGP
Address/Data Bus Strobe-0: This signal provides timing for 2x and 4x
data on AD[15:0] and the C/BE[1:0]# signals. The agent that is providing
the data drives this signal.
AD_STB0#
I/O
(s/t/s)
AGP
Address/Data Bus Strobe-0 Compliment: Differential strobe pair that
provides timing information for the AD[15:0] and C/BE[1:0]# signals. The
agent that is providing the data drives this signal.
AD_STB1
I/O
(s/t/s)
AGP
Address/Data Bus Strobe-1: This signal provides timing for 2x- and 4xclocked data on AD[31:16] and C/BE[3:2]# signals. The agent that is
providing the data drives this signal.
AD_STB1#
I/O
(s/t/s)
AGP
Address/Data Bus Strobe-1 Compliment: The differential compliment
to the AD_STB1 signal. It is used to provide timing for 4x-clocked data.
SB_STB
I
AGP
Sideband Strobe: This signal provides timing for 2x- and 4x- clocked
data on the SBA[7:0] bus. It is driven by the AGP master after the system
has been configured for 2x- or 4x- clocked sideband address delivery.
SB_STB#
I
AGP
Sideband Strobe Compliment: SB_STB# is the differential compliment
to the SB_STB signal. It is used to provide timing for 4x-clocked data.
AGP/PCI Signals
For transactions on the AGP interface carried using AGP FRAME# protocol, these signals operate
similar to their semantics in the PCI 2.1 specification the exact role of all AGP FRAME# signals
are defined below.
Signal Name
26
Type
Description
G_FRAME#
I/O
s/t/s
AGP
FRAME: During FRAME# Operations, G_FRAME# is an output when the
MCH acts as an initiator on the AGP Interface.
G_IRDY#
I/O
s/t/s
AGP
Initiator Ready#: This signal indicates the AGP compliant master is
ready to provide all write data for the current transaction. Once G_IRDY#
is asserted for a write operation, the master is not allowed to insert wait
states. The master is never allowed to insert a wait state during the initial
data transfer (32 bytes) of a write transaction. However, it may insert wait
states after each 32-byte block is transferred.
G_TRDY#
I/O
s/t/s
AGP
Target Ready: This signal indicates the AGP compliant target is ready to
provide read data for the entire transaction (when the transfer size is less
than or equal to 32 bytes) or is ready to transfer the initial or subsequent
block (32 bytes) of data when the transfer size is greater than 32 bytes.
The target is allowed to insert wait states after each block (32 bytes) is
transferred on write transactions.
G_STOP#
I/O
s/t/s
AGP
STOP: G_STOP Is an input when the MCH acts as a FRAME#-based
AGP initiator and an output when the MCH acts as a FRAME#-based
AGP target. G_STOP# is used for disconnect, retry, and abort
sequences on the AGP interface.
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Intel 82845 MCH for SDR Datasheet
Signal Description
R
Signal Name
Type
Description
G_DEVSEL#
I/O
s/t/s
AGP
Device Select: This signal indicates that a FRAME#-based AGP target
device has decoded its address as the target of the current access. The
MCH asserts G_DEVSEL# based on the DRAM address range being
accessed by a PCI initiator. As an input it indicates whether any device
on the bus has been selected.
G_REQ#
I
AGP
Request: Indicates that a FRAME# or PIPE#-based AGP master is
requesting use of the AGP interface. This signal is an input into the
MCH.
G_GNT#
O
AGP
Grant: During SBA, PIPE# and FRAME# operation, G_GNT#, along with
the information on the ST[2:0] signals (status bus), indicates how the
AGP interface will be used next.
G_AD[31:0]
I/O
AGP
Address/Data Bus: These signals are used to transfer both address and
data on the AGP interface.
G_C/BE[3:0]#
I/O
AGP
Command/Byte Enable:
During FRAME# Operation: During the address phase of a transaction,
G_C/BE[3:0]# define the bus command. During the data phase,
G_C/BE[3:0]# are used as byte enables. The byte enables determine
which byte lanes carry meaningful data.
During PIPE# Operation: When an address is enqueued using PIPE#,
the G_C/BE# signals carry command information. The command
encoding used during PIPE#-based AGP is DIFFERENT than the
command encoding used during FRAME#-based AGP cycles (or
standard PCI cycles on a PCI bus).
G_PAR
I/O
AGP
Parity:
During FRAME# Operations: This signal is driven by the MCH when it
acts as a FRAME#-based AGP initiator during address and data phases
for a write cycle, and during the address phase for a read cycle. PAR is
driven by the MCH when it acts as a FRAME#-based AGP target during
each data phase of a FRAME#-based AGP memory read cycle. Even
parity is generated across AD[31:0] and G_C/BE[3:0]#.
During SBA and PIPE# Operation: This signal is not used during SBA
and PIPE# operation.
NOTE: PCIRST# from the ICH2 is connected to RSTIN# and is used to reset AGP interface logic within the
MCH. The AGP agent will also use PCIRST# provided by the ICH2 as an input to reset its internal
logic.
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Intel 82845 MCH for SDR Datasheet
27
Signal Description
R
2.5
Clocks, Reset, and Miscellaneous Signals
Signal Name
BCLK
BCLK#
66IN
Type
Description
I
CMOS
Differential Host Clock In: These pins receive a differential host clock
from the external clock synthesizer. This clock is used by all of the MCH
logic that is in the host clock domain.
I
CMOS
66 MHz Clock In: This pin receives a 66 MHz clock from the clock
synthesizer. This clock is used by AGP/PCI and hub interface clock
domains.
Note: That this clock input is 3.3 V tolerant.
SCK[11:0]
O
CMOS
System Memory Clocks (SDR): These signals deliver a synchronized
clock to the DIMMs. There are two per row.
RSTIN#
I
CMOS
Reset In: When asserted, this signal asynchronously resets the MCH
logic. RSTIN# is connected to the PCIRST# output of the ICH2. All
AGP/PCI output and bi-directional signals will also three-state compliant
to PCI Rev 2.0 and 2.1 specifications.
Note: This input needs to be 3.3 V tolerant.
TESTIN#
I
CMOS
Test Input: This pin is used for manufacturing and board level test
purposes.
Note: This signal has an internal pull-up resistor.
28
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Intel 82845 MCH for SDR Datasheet
Signal Description
R
2.6
Voltage Reference and Power Signals
Signal Name
®
Type
Description
HVREF
Ref
Host Reference Voltage: Reference voltage input for the data, address,
and common clock signals of the host AGTL+ interface.
SDREF
Ref
SDRAM Reference Voltage: Reference voltage input for DQ, DQS,
RDCLKIN (SDR).
HI_REF
Ref
Hub Interface Reference: Reference voltage input for the hub interface.
AGPREF
Ref
AGP Reference: Reference voltage input for the AGP interface.
HLRCOMP
I/O
CMOS
Compensation for Hub Interface: This signal is used to calibrate the
hub interface I/O buffers. It is connected to a 40.2 Ω pull-up resistor with
1% tolerance and is pulled up to VCC1_8.
GRCOMP
I/O
CMOS
Compensation for AGP: This signal is used to calibrate buffers. It is
connected to a 40.2 Ω pull-down resistor with a 1% tolerance.
HRCOMP[1:0]
I/O
CMOS
Compensation for Host: These signals are used to calibrate the host
AGTL+ I/O buffers. Each signal is connected to a 24.9 Ω pull-down
resistor with a 1% tolerance.
HSWNG[1:0]
I
CMOS
Host Reference Voltage: Reference voltage input for the compensation
logic.
SMRCOMP
I/O
CMOS
System Memory RCOMP:
VCC1_5
1.5 V Power Input: These pins are connected to a 1.5 V power source.
VCC1_8
1.8 V Power Input Pins: These pins are connected to a 1.8 V power
source.
VCCSM
SDRAM Power Input Pins: These pins are connected to a 3.3 V power
source for SDR.
VCCA[1:0]
PLL Power Input Pins: These pins provide power for the PLL.
VTT
AGTL+ Bus Termination Voltage Inputs: These pins provide the
AGTL+ bus termination.
VSS
Ground: The VSS pins are the ground pins for the MCH.
VSSA[1:0]
PLL Ground: The VSSA[1:0] pins are the ground pins for the PLL on
the MCH.
Intel 82845 MCH for SDR Datasheet
29
Signal Description
R
2.7
Reset States During Reset
Z
ISO
S
H
L
D
I
Signal Name
Ti-state
Isolate inputs in inactive state
Strap input sampled during assertion or on the de-asserting edge of RSTIN#
Driven high
Driven low
Strong drive (to normal value supplied by core logic if not otherwise stated)
Input active
State
During
RSTIN#
Assertion
System Bus Interface
CPURST#
30
L
Signal Name
State
During
RSTIN#
Assertion
Signal Name
State
During
RSTIN#
Assertion
HLRCOMP
Z
AD_STB[1:0]
Z
HSWNG
I
AD_STB[1:0]#
Z
SB_STB
I
SB_STB#
I
G_AD[31:0]
Z
G_C/BE[3:0]#
Z
G_FRAME#
Z/I
G_IRDY#
Z/I
G_TRDY#
Z/I
G_STOP#
Z/I
G_DEVSEL#
Z/I
G_PAR
Z
AGPREF
Z
SDR System Memory
HADSTB[1:0]#
Z/I
AP[1:0]#
Z/I
SCK[11:0]
Z
HA[31:4]#
Z/I
SCS[11:0]#
Z
HD[63:0]#
Z/I
SMA[12:0]
Z
HDSTBP[3:0]#
Z/I
SBS[1:0]
Z
HDSTBN[3:0]#
Z/I
SRAS#
Z
DBI[3:0]#
Z/I
SCAS#
Z
ADS#
Z/I
SWE#
Z
BNR#
Z/I
SDQ[63:0]
Z/I
BPRI#
Z/I
SCB[7:0]
Z
DBSY#
Z/I
SCKE[5:0]
L
DEFER#
Z/I
RDCLKO
Z
DRDY#
Z/I
RDCLKIN
I
HIT#
Z/I
HITM#
Z/I
HLOCK#
Z/I
HREQ[4:0]#
Z/I
HTRDY#
Z/I
RS[2:0]#
Z/I
BREQ0#
Z/I
HVREF
I
Hub Interface
AGP
PIPE#
SBA[7:0]
I
Z/I
HI_STB
Z/I
HI_STB#
Z/I
Clocks
ISO/S
RBF#
I
WBF#
I/S
G_REQ#
HI_[10:0]
BCLK
I
Miscellaneous
I
ST[2:0]
L/S
G_GNT#
H/S
®
RSTIN#
I
TESTIN#
I
Intel 82845 MCH for SDR Datasheet
Register Description
R
3
Register Description
The MCH contains two sets of software accessible registers, accessed via the host processor I/O
address space:
• Control registers I/O mapped into the processor I/O space, which control access to PCI and
AGP configuration space (see Section 3.3).
• Internal configuration registers residing within the MCH are partitioned into two logical
device register sets (“logical” since they reside within a single physical device). The first
register set is dedicated to Host-HI Bridge functionality (i.e., DRAM configuration, other
chip-set operating parameters and optional features). The second register block is dedicated to
Host-AGP Bridge functions (controls AGP interface configurations and operating
parameters).
The MCH supports PCI configuration space accesses using the mechanism denoted as
Configuration Mechanism #1 in the PCI specification.
The MCH internal registers (I/O Mapped and configuration registers) are accessible by the
processor. The registers can be accessed as Byte, Word (16-bit), or DWord (32-bit) quantities,
with the exception of CONF_ADDR which can only be accessed as a DWord. All multi-byte
numeric fields use "little-endian" ordering (i.e., lower addresses contain the least significant parts
of the field).
3.1
Register Terminology
Term
®
Description
RO
Read Only. If a register is read only, writes to this register have no effect.
R/W
Read/Write. A register with this attribute can be read and written.
R/W/L
Read/Write/Lock. A register with this attribute can be read, written, and Locked.
R/WC
Read/Write Clear. A register bit with this attribute can be read and written. However, a
write of a 1 clears (sets to 0) the corresponding bit and a write of a 0 has no effect.
R/WO
Read/Write Once. A register bit with this attribute can be written to only once after
power up. After the first write, the bit becomes read only.
L
Lock. A register bit with this attribute becomes Read Only after a lock bit is set.
Reserved Bits
Some of the MCH registers described in this section contain reserved bits. These bits
are labeled “Reserved”. Software must deal correctly with fields that are reserved. On
reads, software must use appropriate masks to extract the defined bits and not rely on
reserved bits being any particular value. On writes, software must ensure that the
values of reserved bit positions are preserved. That is, the values of reserved bit
positions must first be read, merged with the new values for other bit positions and
then written back. Note that software does not need to perform a read-merge-write
operation for the Configuration Address (CONF_ADDR) register.
Intel 82845 MCH for SDR Datasheet
31
Register Description
R
Term
3.2
Description
Reserved
Registers
In addition to reserved bits within a register, the MCH contains address locations in the
configuration space that are marked “Reserved”. When a “Reserved” register location
is read, a random value is returned. (“Reserved” registers can be 8-, 16-, or 32-bit in
size). Registers that are marked as “Reserved” must not be modified by system
software. Writes to “Reserved” registers may cause system failure.
Default Value
upon a Reset
Upon a Full Reset, the MCH sets all of its internal configuration registers to
predetermined default states. Some register values at reset are determined by
external strapping options. The default state represents the minimum functionality
feature set required to successfully bring up the system. Hence, it does not represent
the optimal system configuration. It is the responsibility of the system initialization
software (usually BIOS) to properly determine the DRAM configurations, operating
parameters and optional system features that are applicable, and to program the MCH
registers accordingly.
PCI Bus Configuration Space Access
The MCH and ICH2 are physically connected by the hub interface. From a configuration
standpoint, the hub interface is PCI bus 0. As a result, all devices internal to the MCH and ICH2
appear to be on PCI bus 0. The system’s primary PCI expansion bus is physically attached to the
ICH2 and, from a configuration perspective appears to be a hierarchical PCI bus behind a PCI-toPCI bridge and, therefore, has a programmable PCI Bus number. Note that the primary PCI bus
is referred to as PCI_A in this document and is not PCI bus #0 from a configuration
standpoint. The AGP appears to system software to be a real PCI bus behind PCI-to-PCI bridges
resident as devices on PCI bus 0.
The MCH contains two PCI devices within a single physical component. The configuration
registers for the four devices are mapped as devices residing on PCI bus 0.
• Device 0: Host-Hub Interface Bridge/DRAM Controller. Logically this appears as a PCI device
residing on PCI bus 0. Physically Device 0 contains the standard PCI registers, DRAM registers, the
Graphics Aperture controller, and other MCH specific registers.
• Device 1: Host-AGP Bridge. Logically this appears as a “virtual” PCI-to-PCI bridge residing
on PCI bus 0. Physically Device 1 contains the standard PCI-to-PCI bridge registers and the
standard AGP/PCI configuration registers (including the AGP I/O and memory address
mapping).
Table 6 shows the Device # assignment for the various internal MCH devices.
®
Table 6. Intel MCH Internal Device Assignments
MCH Function
Bus 0, Device #
DRAM Controller/8 bit HI_A Controller
Device 0
Host-to-AGP Bridge (virtual P2P)
Device 1
NOTE: A physical PCI bus 0 does not exist. The hub interface and the internal devices in
the MCH and ICH2, logically constitute PCI Bus 0 to configuration software.
32
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Intel 82845 MCH for SDR Datasheet
Register Description
R
3.2.1
Standard PCI Bus Configuration Mechanism
The PCI Bus defines a slot based "configuration space" that allows each device to contain up to 8
functions with each function containing up to 256 8-bit configuration registers. The PCI
specification defines two bus cycles to access the PCI configuration space: Configuration Read
and Configuration Write. Memory and I/O spaces are supported directly by the processor.
Configuration space is supported by a mapping mechanism implemented within the MCH. The
PCI specification defines two mechanisms to access configuration space, Mechanism #1 and
Mechanism #2. The MCH supports only Mechanism #1.
The configuration access mechanism makes use of the CONF_ADDR Register (at I/O address
0CF8h though 0CFBh) and CONF_DATA register (at I/O address 0CFCh though 0CFFh). To
reference a configuration register a DWord I/O write cycle is used to place a value into
CONF_ADDR that specifies the PCI bus, the device on that bus, the function within the device,
and a specific configuration register of the device function being accessed. CONF_ADDR[31]
must be 1 to enable a configuration cycle. CONF_DATA then becomes a window into the four
bytes of configuration space specified by the contents of CONF_ADDR. Any read or write to
CONF_DATA results in the MCH translating the CONF_ADDR into the appropriate
configuration cycle.
The MCH is responsible for translating and routing the processor’s I/O accesses to the
CONF_ADDR and CONF_DATA registers to internal MCH configuration registers, hub interface
or AGP.
3.2.2
Routing Configuration Accesses
The MCH supports two bus interfaces: the hub interface and AGP. PCI configuration cycles are
selectively routed to one of these interfaces. The MCH is responsible for routing PCI configuration
cycles to the proper interface. PCI configuration cycles to the ICH2 internal devices and Primary
PCI (including downstream devices) are routed to the ICH2 via the hub interface. AGP
configuration cycles are routed to AGP. The AGP interface is treated as a separate PCI bus from
the configuration point of view. Routing of configuration AGP is controlled via the standard PCIPCI bridge mechanism using information contained within the Primary Bus Number, the
Secondary Bus Number, and the Subordinate Bus Number registers of the corresponding PCI-PCI
bridge device.
A detailed description of the mechanism for translating processor I/O bus cycles to configuration
cycles on one of the buses is described below.
PCI Bus 0 Configuration Mechanism
The MCH decodes the Bus Number (bits 23:16) and the Device Number fields of the
CONF_ADDR register. If the Bus Number field of CONF_ADDR is 0, the configuration cycle is
targeting a PCI Bus 0 device.
• The Host-HI Bridge entity in the MCH is hardwired as Device 0 on PCI Bus 0.
• The Host-AGP Bridge entity in the MCH is hardwired as Device 1 on PCI Bus 0.
Configuration cycles to any of the MCH’s internal devices are confined to the MCH and not sent
over the hub interface. Accesses to disabled MCH internal devices are forwarded over the hub
interface as Type 0 Configuration Cycles.
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Intel 82845 MCH for SDR Datasheet
33
Register Description
R
Primary PCI and Downstream Configuration Mechanism
If the Bus Number in the CONF_ADDR is non-zero, and is less than the value in the Host-AGP
device’s Secondary Bus Number register, or greater than the value in the Host-AGP device’s
Subordinate Bus Number register, the MCH will generate a Type 1 hub interface configuration
cycle. The ICH2 compares the non-zero Bus Number with the Secondary Bus Number and
Subordinate Bus Number registers of its P2P bridges to determine if the configuration cycle is
meant for Primary PCI, or a downstream PCI bus.
AGP Configuration Mechanism
From the chip-set configuration perspective, AGP is seen as a PCI bus interface residing on a
Secondary Bus side of the “virtual” PCI-PCI bridges referred to as the MCH Host-AGP bridge. On
the Primary Bus side, the “virtual” PCI-PCI bridge is attached to PCI Bus 0. Therefore, the
Primary Bus Number register is hardwired to 0. The “virtual” PCI-PCI bridge entity converts
Type 1 PCI bus configuration cycles on PCI Bus 0 into Type 0 or Type 1 configuration cycles on
the AGP interface. Type 1 configuration cycles on PCI Bus 0 that have a Bus Number that
matches the Secondary Bus Number of the MCH’s “virtual” Host-to-PCI_B/AGP bridge will be
translated into Type 0 configuration cycles on the AGP interface.
If the Bus Number is non-zero, greater than the value programmed into the Secondary Bus
Number Register, and less than or equal to the value programmed into the Subordinate Bus
Number Register, the MCH will generate a Type 1 PCI configuration cycle on AGP.
3.3
I/O Mapped Registers
The MCH contains two registers that reside in the processor I/O address space: the Configuration
Address (CONF_ADDR) register and the Configuration Data (CONF_DATA) register. The
Configuration Address register enables/disables the configuration space and determines what
portion of configuration space is visible through the configuration data window.
3.3.1
CONF_ADDR—Configuration Address Register
I/O Address:
Default Value:
Access:
Size:
0CF8h Accessed as a DWord
00000000h
R/W
32 bits
CONF_ADDR is a 32 bit register that can be accessed only as a DWord. A Byte or Word
reference will "pass through" the Configuration Address register and the hub interface, onto the
PCI bus as an I/O cycle. The CONF_ADDR register contains the Bus Number, Device Number,
Function Number, and Register Number for which a subsequent configuration access is intended.
34
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Intel 82845 MCH for SDR Datasheet
Register Description
R
Bit
31
Descriptions
Configuration Enable (CFGE).
0 = Disable.
1 = Enable. Accesses to PCI configuration space are enabled.
30:24
Reserved. These bits are read only and have a value of 0.
23:16
Bus Number. When Bus Number is programmed to 00h, the target of the configuration cycle is
a hub interface agent (MCH, ICH2, etc.).
The configuration cycle is forwarded to the hub interface, if Bus Number is programmed to 00h
and the MCH is not the target (the device number is ≥2).
If Bus Number is non-zero and matches the value programmed into the Secondary Bus Number
Register of device 1, a Type 0 PCI configuration cycle will be generated on AGP.
If Bus Number is non-zero, greater than the value in the Secondary Bus Number register of
device 1 and less than or equal to the value programmed into the Subordinate Bus Number
register of device 1 a Type 1 PCI configuration cycle will be generated on AGP.
If Bus Number is non-zero, and does not fall within the ranges enumerated by device 1’s
Secondary Bus Number or Subordinate Bus Number register, then a hub interface Type 1
configuration cycle is generated.
15:11
Device Number. This field selects one agent on the PCI bus selected by the Bus Number field.
When the Bus Number field is 00, the MCH decodes the Device Number field. The MCH is
always Device Number 0 for the Host-Hub Interface bridge entity and Device Number 1 for the
Host-AGP entity. Therefore, when Bus Number =0 and Device Number=0–1, the internal MCH
devices are selected.
If the Bus Number is non-zero and matches the value programmed into the Secondary Bus
Number register a Type 0 PCI configuration cycle is generated on AGP. The MCH decodes the
Device Number field ([15:11]) and assert the appropriate GAD signal as an IDSEL. For PCI-toPCI Bridge translation, one of the 16 IDSELs is generated. When bit [15] = 0, bits [14:11] are
decoded to assert a signal AD[31:16] IDSEL. GAD16 is asserted to access Device 0, GAD17 for
Device 1, and so forth up to Device 15 which asserts AD31. All device numbers higher than 15
cause a type 0 configuration access with no IDSEL asserted, which results in a Master Abort
reported in the MCH’s “virtual” PCI-PCI bridge registers.
For Bus Numbers resulting in hub interface configuration cycles, the MCH propagates the device
number field as A[15:11]. For bus numbers resulting in AGP type 1 configuration cycles, the
device number is propagated as GAD[15:11].
®
10:8
Function Number. This field is mapped to GAD[10:8] during AGP configuration cycles and
A[10:8] during Hub Interface configuration cycles. This allows the configuration registers of a
particular function in a multi-function device to be accessed. The MCH ignores configuration
cycles to its internal devices if the function number is not equal to 0.
7:2
Register Number. This field selects one register within a particular bus, device, and function as
specified by the other fields in the Configuration Address register. This field is mapped to
GAD[7:2] during AGP configuration cycles and A[7:2] during hub interface configuration cycles.
1:0
Reserved.
Intel 82845 MCH for SDR Datasheet
35
Register Description
R
3.3.2
CONF_DATA—Configuration Data Register
I/O Address:
Default Value:
Access:
Size:
0CFCh
00000000h
R/W
32 bits
CONF_DATA is a 32 bit read/write window into configuration space. The portion of
configuration space that is referenced by CONF_DATA is determined by the contents of
CONF_ADDR.
3.4
Bit
Descriptions
31:0
Configuration Data Window (CDW). If bit 31 of the CONF_ADDR register is 1, any I/O access
to the CONF_DATA register will be mapped to configuration space using the contents of
CONF_ADDR.
Memory-Mapped Register Space
All system memory control functions have been consolidated into a new memory-mapped address
region within Device 0, Function 0. This space will be accessed using a new Base Address register
(BAR) located at Device 0, Function 0 (address offset 14h). By default this BAR is invisible
(i.e., read-only as 0s).
Note: All accesses to these memory-mapped registers must be made as a single DWord (4 bytes) or less.
Access must be aligned on a natural boundary.
The high-level address map for the memory-mapped registers is shown in Table 7.
Table 7. Memory-mapped Register Address Map
Memory Address Offset
36
Register Group
020h–02Bh
Reserved
2Ch
DRAM Width Register
02Dh–02Fh
Reserved
030h–034h
Strength Registers
040h–0DFh
Reserved
140h–1DFh
Reserved
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.4.1
DRAMWIDTH—DRAM Width Register
Address Offset:
Default Value:
Access:
Size:
2Ch
00h
R/W
8 bits
This register determines the width of SDRAM devices populated in each row of memory.
Bit
7:6
Descriptions
Reserved.
5
Row 5 Width. Width of devices in Row 5
0 = 16-bit wide devices, or Unpopulated (default)
1 = 8-bit wide devices
4
Row 4 Width. Width of devices in Row 4
0 = 16-bit wide devices, or Unpopulated (default)
1 = 8-bit wide devices
3
Row 3 Width. Width of devices in Row 3
0 = 16-bit wide devices, or Unpopulated (default)
1 = 8-bit wide devices
2
Row 2 Width. Width of devices in Row 2
0 = 16-bit wide devices, or Unpopulated (default)
1 = 8-bit wide devices
1
Row 1 Width. Width of devices in Row 1
0 = 16-bit wide devices, or Unpopulated (default)
1 = 8-bit wide devices
0
Row 0 Width. Width of devices in Row 0
0 = 16-bit wide devices, or Unpopulated (default)
1 = 8-bit wide devices
Note: Since there are multiple clock signals assigned to each row of a DIMM, it is important to clarify
exactly which row width field affects which clock signal.
®
Row Parameters
SDR Clocks Affected
0
SCK[0], SCK[2]
1
SCK[1], SCK[3]
2
SCK[4], SCK[6]
3
SCK[5], SCK[7]
4
SCK[8], SCK[10]
5
SCK[9], SCK[11]
Intel 82845 MCH for SDR Datasheet
37
Register Description
R
3.4.2
DQCMDSTR—Strength Control Register (SDQ and CMD
Signal Groups)
Memory Address Offset:
Default Value:
Access:
Size:
30h
00h
R/W
8 bits
This register controls the drive strength of the I/O buffers for the DQ/DQS and CMD signal
groups.
Bit
7
6:4
Descriptions
Reserved.
CMD Strength Control (SRAS#, SCAS#, SWE#, SMA[12:0], SBS[1:0]). This field selects the
signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
3
2:0
Reserved.
SDQ/SDQS Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
38
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.4.3
CKESTR—Strength Control Register (SCKE Signal Group)
Memory Address Offset:
Default Value:
Access:
Size:
31h
00h
R/W
8 bits
This register controls the drive strength of the I/O buffers for the CKE signal group. This group
has two possible loadings depending on the width of SDRAM devices used in each row of memory
(x8 or x16). The proper strength can be independently programmed for each configuration. The
actual strength used for each signal is determined by the DRAMWIDTH Register (offset 2Ch).
Bit
7
6:4
Descriptions
Reserved.
SCKE x16 Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
3
2:0
Reserved.
SCKE x8 Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
®
Intel 82845 MCH for SDR Datasheet
39
Register Description
R
3.4.4
CSBSTR—Strength Control Register (SCS# Signal Group)
Memory Address Offset:
Default Value:
Access:
Size:
32h
00h
R/W
8 bits
This register controls the drive strength of the I/O buffers for the SCS# signal group. This group
has two possible loadings depending on the width of SDRAM devices used in each row of memory
(x8 or x16). The proper strength can be independently programmed for each configuration. The
actual strength used for each signal is determined by the DRAMWIDTH Register (offset 2Ch).
Bit
7
6:4
Descriptions
Reserved.
SCS# x16 Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
3
2:0
Reserved.
SCS# x8 Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
40
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.4.5
CKSTR—Strength Control Register (Clock Signal Group)
Memory Address Offset:
Default Value:
Access:
Size:
33h
00h
R/W
8 bits
This register controls the drive strength of the I/O buffers for the Clock (CK) signal group
including both the CK and CK# signals. This group has two possible loadings depending on the
width of SDRAM devices used in each row of memory (x8 or x16). The proper strength can be
independently programmed for each configuration. The actual strength used for each signal is
determined by the DRAMWIDTH Register (offset 2Ch).
Bit
7
6:4
Descriptions
Reserved.
CK x16 Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
3
2:0
Reserved.
CK x8 Strength Control. This field selects the signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
®
Intel 82845 MCH for SDR Datasheet
41
Register Description
R
3.4.6
RCVENSTR—Strength Control Register (RCVENOUT
Signal Group)
Memory Address Offset:
Default Value:
Access:
Size:
34h
00h
R/W
8 bits
This register controls the drive strength of the I/O buffers for the Receive Enable Out signal group
(RDCLKO# signal).
Bit
Descriptions
7:3
Reserved.
2:0
Receive Enable Out Signal Group (RCVEnOut) Strength Control. This field selects the
signal drive strength.
000 = 0.75 X (default)
001 = 1.00 X
010 = 1.25 X
011 = 1.50 X
100 = 2.00 X
101 = 2.50 X
110 = 3.00 X
111 = 4.00 X
42
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5
Host-Hub Interface Bridge Device Registers
(Device 0)
Table 8 provides the register address map for Device 0 PCI configuration space. An “s” in the
Default Value column indicates that a strap determines the power-up default value for that bit.
®
Table 8. Intel MCH Configuration Space (Device 0)
®
Address
Offset
Register
Symbol
00–01h
VID
Vendor Identification
8086h
RO
02–03h
DID
Device Identification
1A30h
RO
04–05h
PCICMD
PCI Command
0006h
RO, R/W
06–07h
PCISTS
PCI Status
0090h
RO, R/WC
08h
RID
Revision Identification
03h, 04h
RO
09h
—
Reserved.
—
—
0Ah
SUBC
Sub-Class Code
00h
RO
0Bh
BCC
Base Class Code
06h
RO
0Dh
MLT
Master Latency Timer
00h
RO
0Eh
HDR
Header Type
00h
RO
0Fh
—
Reserved.
—
—
10–13h
APBASE
Aperture Base Configuration
00000008h
RO, R/W
14–2Bh
—
Reserved.
—
—
2C–2Dh
SVID
Subsystem Vendor Identification
0000h
R/WO
2E–2Fh
SID
Subsystem Identification
0000h
R/WO
30–33h
—
Reserved.
—
—
34h
CAPPTR
Capabilities Pointer
A0h
RO
35–50h
—
Reserved.
—
—
51h
AGPM
AGP Miscellaneous Configuration
00h
R/W
52–5Fh
—
Reserved.
—
—
60–67h
DRB[0:7]
DRAM Row Boundary (8 registers)
00h
R/W
68–6Fh
—
Reserved.
—
—
70–73h
DRA
DRAM Row Attribute (4 registers)
00h
R/W
73–77h
—
Reserved.
—
—
78–7Bh
DRT
DRAM Timing Register
00000010h
R/W
7C–7Fh
DRC
DRAM Controller Mode
0000h
R/W, RO
80–85h
—
Reserved.
—
—
86h
DERRSYN
DRAM Error Syndrome
00h
RO
Intel 82845 MCH for SDR Datasheet
Register Name
Default
Value
Access
43
Register Description
R
Address
Offset
Register
Symbol
87–8Bh
—
8C–8Fh
EAP
90–96h
PAM[0:6]
97h
FDHC
98–9Ch
—
9Dh
SMRAM
9Eh
ESMRAMC
9Fh
—
A0–A3h
ACAPID
A4–A7h
Default
Value
Access
Reserved.
—
—
Error Address Pointer
00000000h
RO
Programmable Attribute Map (7 Registers)
0000000000
0000h
RO, R/W
Fixed DRAM Hole Control
00h
R/W
Reserved.
—
—
System Management RAM Control
02h
RO, R/W,
R/W/L
Extended System Mgmt RAM Control
38h
RO, R/W,
R/WC,
R/W/L
Reserved.
—
—
AGP Capability Identifier
00200002h
RO
AGPSTAT
AGP Status
1F000216h
RO
A8–ABh
AGPCMD
AGP Command
00000000h
R/W
AC–AFh
—
Reserved.
—
—
B0–B3h
AGPCTRL
AGP Control
00000000h
R/W
B4h
APSIZE
Aperture Size
00h
R/W
B5–B7h
—
Reserved
—
—
B8–BBh
ATTBASE
Aperture Translation Table Base
00000000h
R/W
BCh
AMTT
AGP MTT Control
00h
R/W
BDh
LPTT
AGP Low Priority Transaction Timer
00h
R/W
BE–C3h
44
Register Name
Reserved
C4–C5h
TOM
Top of Low Memory
0000h
R/W
C6–C7h
MCHCFG
MCH Configuration
0000h
R/W, RO
C8–C9h
ERRSTS
Error Status
0000h
R/WC
CA–CBh
ERRCMD
Error Command
0000h
R/W
CC–CDh
SMICMD
SMI Command
0000h
R/W
CE–CFh
SCICMD
SCI Command
0000h
R/W
D0–DDh
—
Reserved.
—
—
DE–DFh
SKPD
Scratchpad Data
0000h
R/W
E0–E3h
—
Reserved.
—
—
E4–E7h
CAPID
Product Specific Capability Identifier
F104A009h
RO
E8–FFh
—
Reserved.
—
—
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.1
VID—Vendor Identification Register (Device 0)
Address Offset:
Default Value:
Attribute:
Size:
00–01h
8086h
RO
16 bits
The VID Register contains the vendor identification number. This 16-bit register combined with
the DID Register uniquely identifies any PCI device. Writes to this register have no effect.
Bit
15:0
Description
Vendor Identification Number. This is a 16-bit value assigned to Intel.
Intel VID = 8086h.
3.5.2
DID—Device Identification Register (Device 0)
Address Offset:
Default Value:
Attribute:
Size:
02–03h
1A30h
RO
16 bits
This 16-bit register combined with the VID Register uniquely identifies any PCI device. Writes to
this register have no effect.
Bit
15:0
®
Description
Device Identification Number. This is a 16-bit value assigned to the MCH Host-Hub Interface
Bridge Function #0.
Intel 82845 MCH for SDR Datasheet
45
Register Description
R
3.5.3
PCICMD—PCI Command Register (Device 0)
Address Offset:
Default:
Access:
Size
04–05h
0006h
R/W, RO
16 bits
Since MCH Device 0 does not physically reside on PCI0, many of the bits are not implemented.
Bit
15:10
Descriptions
Reserved.
9
Fast Back-to-Back—RO. Not implemented; Hardwired to 0. This bit controls whether or not the
master can do fast back-to-back write. Since device 0 is strictly a target this bit is not
implemented.
8
SERR Enable (SERRE)—R/W. This bit is a global enable bit for Device 0 SERR messaging.
The MCH does not have an SERR# signal. The MCH communicates the SERR# condition by
sending a SERR message to the ICH2.
0 =Disable. SERR message is not generated by the MCH for Device 0.
1 =Enable. The MCH is enabled to generate SERR messages over the hub interface for
specific Device 0 error conditions that are individually enabled in the ERRCMD Register. The
error status is reported in the ERRSTS and PCISTS registers.
NOTE: This bit only controls SERR message for the Device 0. Device 1 has its own SERRE
bits to control error reporting for error conditions occurring on their respective devices.
46
7
Address/Data Stepping—RO. Not implemented; Hardwired to 0.
6
Parity Error Enable (PERRE)—RO. Not implemented; Hardwired to 0.The PERR# signal is not
implemented by the MCH.
5
VGA Palette Snoop—RO. Not implemented; Hardwired to 0.
4
Memory Write and Invalidate Enable(MWIE)—RO. Not implemented; Hardwired to 0.
3
Special Cycle Enable(SCE)—RO. Not implemented; Hardwired to 0.
2
Bus Master Enable (BME)—RO. Hardwired to 1. The MCH is always enabled as a master on
the hub interface.
1
Memory Access Enable (MAE)—RO. Not implemented; Hardwired to 1. The MCH always
allows access to system memory.
0
I/O Access Enable (IOAE)—RO. Not implemented; Hardwired to 0.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.4
PCISTS—PCI Status Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
06–07h
0090h
RO, R/WC
16 bits
PCISTS is a 16-bit status register that reports the occurrence of error events on Device 0s on the
hub interface. Since MCH Device 0 is the Host-to-hub interface bridge, many of the bits are not
implemented.
Bit
Description
15
Reserved.
14
Signaled System Error (SSE)—R/WC.
0 = Software clears this bit by writing a 1 to it.
1 = MCH Device 0 generated an SERR message over the hub interface for any enabled Device
0 error condition. Device 0 error conditions are enabled in the PCICMD and ERRCMD
Registers. Device 0 error flags are read/reset from the PCISTS or ERRSTS Registers.
13
Received Master Abort Status (RMAS)—R/WC.
0 = Software clears this bit by writing a 1 to it.
1 = MCH generated a hub interface request that receives a Master Abort completion packet or
Master Abort Special Cycle.
12
Received Target Abort Status (RTAS)—R/WC.
0 = Software clears this bit by writing a 1 to it.
1 = MCH generated a hub interface request that receives a Target Abort completion packet or
Target Abort Special Cycle.
11
10:9
Signaled Target Abort Status (STAS)—RO. Not Implemented; Hardwired to 0. The MCH will
not generate a Target Abort hub interface completion packet or special cycle.
DEVSEL Timing (DEVT)—RO. Hardwired to 00. Hub interface does not comprehend
DEVSEL# protocol.
8
Master Data Parity Error Detected (DPD)—RO. Not Implemented; Hardwired to 0. PERR
signaling and messaging are not implemented by the MCH.
7
Fast Back-to-Back (FB2B)—RO. Hardwired to 1.
6:5
4
Reserved.
Capability List (CLIST)—RO.
1 = Indicates to the configuration software that this device/function implements a list of new
capabilities. A list of new capabilities is accessed via the CAPPTR Register (offset 34h).
CAPPTR contains an offset pointing to the start address within configuration space of this
device where the AGP Capability standard register resides.
3:0
®
Reserved.
Intel 82845 MCH for SDR Datasheet
47
Register Description
R
3.5.5
RID—Revision Identification Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
08h
See table below
RO
8 bits
This register contains the revision number of the MCH Device 0. These bits are read only and
writes to this register have no effect.
Bit
Description
7:0
Revision Identification Number. This is an 8-bit value that indicates the revision identification
number for the MCH Device 0.
03h = A3 Stepping
04h = B0 Stepping
3.5.6
SUBC—Sub-Class Code Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
0Ah
00h
RO
8 bits
This register contains the Sub-Class Code for the MCH Device 0.
Bit
7:0
Description
Sub-Class Code (SUBC). This is an 8-bit value that indicates the category of bridge of the
MCH.
00h = Host bridge.
3.5.7
BCC—Base Class Code Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
0Bh
06h
RO
8 bits
This register contains the Base Class Code of the MCH Device 0.
Bit
7:0
Description
Base Class Code (BASEC). This is an 8-bit value that indicates the Base Class Code for the
MCH.
06h = Bridge device.
48
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.8
MLT—Master Latency Timer Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
0Dh
00h
RO
8 bits
The hub interface does not comprehend the concept of Master Latency Timer. Therefore, this
register is not implemented.
Bit
7:0
3.5.9
Description
Hardwired to 00h. Writes have no effect.
HDR—Header Type Register (Device 0)
Address Offset:
Default:
Access:
Size:
0Eh
00h
RO
8 bits
This register identifies the header layout of the configuration space.
Bit
7:0
®
Description
Hardwired to 00h. Writes have no effect.
Intel 82845 MCH for SDR Datasheet
49
Register Description
R
3.5.10
APBASE—Aperture Base Configuration Register (Device 0)
Offset:
Default:
Access:
Size:
10–13h
0000_0008h
R/W, RO
32 bits
The APBASE is a standard PCI Base Address register that is used to set the base of the Graphics
Aperture. The standard PCI Configuration mechanism defines the base address configuration
register such that only a fixed amount of space can be requested (dependent on which bits are
hardwired to 0 or behave as hardwired to 0). To allow for flexibility (of the aperture), an
additional register called APSIZE is used as a “back-end” register to control, which bits of the
APBASE will behave as hardwired to 0. This register will be programmed by the MCH specific
BIOS code that runs before any of the generic configuration software is run.
Note: Bit 9 of the MCHCFG register is used to prevent accesses to the aperture range before this register
is initialized by the configuration software and the appropriate translation table structure has been
established in the system memory.
Bit
31:28
Description
Upper Programmable Base Address—R/W. These bits are part of the aperture base set by
configuration software to locate the base address of the graphics aperture. They correspond to
bits [31:28] of the base address in the processor's address space that will cause a graphics
aperture translation to be inserted into the path of any memory read or write.
Default = 0000
27:22
Middle “Hardwired”/Programmable Base Address—R/W. These bits are part of the aperture
base set by configuration software to locate the base address of the graphics aperture. They
correspond to bits [27:4] of the base address in the processor's address space that will cause a
graphics aperture translation to be inserted into the path of any memory read or write. These
bits can behave as though they were hardwired to 0, if programmed to do so by the APSIZE bits
of the APSIZE register. This causes configuration software to understand that the granularity of
the graphics aperture base address is either finer or more coarse, depending on the bits set by
MCH-specific configuration software in APSIZE.
21:4
Lower “Hardwired” Base Address—RO. Hardwired to 0s. This forces a minimum aperture
size selected by this register to be 4 MB.
3
Prefetchable—RO. This bit is hardwired to 1 to identify the Graphics Aperture range as
prefetchable as per the PCI Local Bus Specification for the base address registers.
There are no side effects on reads, the device returns all bytes on reads, regardless of the byte
enables, and the MCH may merge processor writes into this range without causing errors.
2:1
0
50
Type—RO. These bits determine addressing type and they are hardwired to “00” to indicate that
address range defined by the upper bits of this register can be located anywhere in the 32-bit
address space.
Memory Space Indicator—RO. Hardwired to 0 to identify aperture range as a memory range.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.11
SVID—Subsystem Vendor Identification (Device 0)
Offset:
Default:
Access:
Size:
2C–2Dh
0000h
R/WO
16 bits
This value is used to identify the vendor of the subsystem.
Bit
15:0
3.5.12
Description
Subsystem Vendor ID. (Default = 0000h). This field should be programmed during boot-up.
After this field is written once, it becomes read only.
SID—Subsystem Identification (Device 0)
Offset:
Default:
Access:
Size:
2E–2Fh
0000h
R/WO
16 bits
This value is used to identify a particular subsystem.
Bit
15:0
3.5.13
Description
Subsystem ID. (Default = 0000h). This field should be programmed during boot-up. After this
field is written once, it becomes read only.
CAPPTR—Capabilities Pointer (Device 0)
Offset:
Default:
Access:
Size:
34h
E4h
RO
8 bits
The CAPPTR provides the offset that is the pointer to the location where the AGP standard
registers are located.
Bit
7:0
Description
AGP Standard Register Block Pointer Address. This address pointer indicates to software
where it can find the beginning of the AGP register block.
E4h = AGP register block beginning address.
®
Intel 82845 MCH for SDR Datasheet
51
Register Description
R
3.5.14
AGPM—AGP Miscellaneous Configuration Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
Bit
7:2
1
3.5.15
51h
00h
R/W
8 bits
Descriptions
Reserved.
Aperture Access Global Enable (APEN). This bit is used to prevent access to the graphics
aperture from any port (processor, hub interface, or AGP/PCI_B) before the aperture range is
established by the configuration software and the appropriate translation table in system
memory has been initialized. The default value is 0; thus, this field must be set after system is
fully configured to enable aperture accesses.
DRB[0:7]—DRAM Row Boundary Registers (Device 0)
Offset:
Default:
Access:
Size:
60–67h (DRB0–DRB7)
00h
R/W
8 bits
The DRAM Row Boundary Register defines the upper boundary address of each pair of DRAM
rows with a granularity of 32 MB. Each row has its own single-byte DRB register. For example, a
value of 1 in DRB0 indicates that 32 MB of DRAM has been populated in the first row.
Row 0 = 60h
Row 1 = 61h
Row 2 = 62h
Row 3 = 63h
Row 4 = 64h
Row 5 = 65h (See Note 1)
Row 6 = 66h (See Note 2)
Row 7 = 67h (See Note 2)
DRB0 = Total memory in row0 (in 32 MB increments)
DRB1 = Total memory in row0 + row1 (in 32 MB increments)
Notes:
1. DRB5 = Total memory in row0 + row1 + row2 + row3 + row4 + row5 (in 32 MB increments)
2. DRB [7:6] must be programmed with the value contained in DBR5
Each Row is represented by a byte. Each byte has the following format.
Bit
7:0
52
Description
DRAM Row Boundary Address. This 8 bit value defines the upper and lower addresses for
each DRAM row. This 8-bit value is compared against a set of address lines to determine the
upper address limit of a particular row.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.16
DRA—DRAM Row Attribute Registers (Device 0)
Offset:
Default:
Access:
Size:
70–73h (DRA0–DRA3)
00h
R/W
8 bits
The DRAM Row Attribute Register defines the page sizes to be used when accessing different
pairs of rows. Each nibble of information in the DRA registers describes the page size of a pair of
rows:
Row 0, 1 = 70h
Row 2, 3 = 71h
Row 4, 5 = 72h (Used for SDRAM configuration only)
Row 6, 7 = 73h (RAODD and RAEVEN fields must contain default value of 00h)
7
6
Rsvd
7
Row attribute for Row 1
6
Rsvd
7
Rsvd
®
4
6
Row attribute for Row 5
Intel 82845 MCH for SDR Datasheet
3
3
3
Rsvd
0
Row Attribute for Row 0
2
0
Row Attribute for Row 2
2
Rsvd
4
Row attribute for Row 7
2
Rsvd
4
6
3
Rsvd
Row attribute for Row 3
Rsvd
7
4
0
Row Attribute for Row 4
2
0
Row Attribute for Row 6
53
Register Description
R
Bit
7
6:4
Description
Reserved.
Row Attribute for Odd-Numbered Row (RAODD). This 3-bit field defines the page size of the
corresponding row.
001 = 2 KB
010 = 4 KB
011 = 8 KB
100 = 16 KB
Others = Reserved
3
Reserved.
2:0
Row Attribute for Even-Numbered Row (RAEVEN). This 3-bit field defines the page size of
the corresponding row.
001 = 2 KB
010 = 4 KB
011 = 8 KB
100 = 16 KB
Others = Reserved
54
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.17
DRT—DRAM Timing Register (Device 0)
Offset:
Default:
Access:
Size:
78–7Bh
00000010h
R/W
32 bits
Bit
Description
31:19
Reserved.
18:16
DRAM Idle Timer. This field determines the number of clocks the DRAM controller will remain
in the idle state before it begins precharging all pages.
000 = infinite.
001 = 0 DRAM clocks
010 = 8 DRAM clocks
011 = 16 DRAM clocks
100 = 64 DRAM clocks
Others = Reserved
15:11
Reserved.
10:9
Activate to Precharge delay (tRAS). This bit controls the number of DRAM clocks for tRAS.
00 = 7 clocks
01 = 6 clocks
10 = 5 clocks
11 = Reserved
8:6
Reserved.
5:4
CAS# Latency (tCL). This bit controls the number of DRAM clocks between when a read
command is sampled by the SDRAMs and when the MCH samples read data from the
SDRAMs.
00 = Reserved
01 = 3 clocks
10 = 2 clocks
11 = Reserved
3
Reserved.
2
DRAM RAS# to CAS# Delay (tRCD). This bit controls the number of clocks inserted between a
row activate command and a read or write command to that row.
0 = 3 DRAM clocks
1 = 2 DRAM clocks
1
Reserved.
0
DRAM RAS# Precharge (tRP). This bit controls the number of clocks that are inserted
between a row precharge command and an activate command to the same row.
0 = 3 DRAM clocks
1 = 2 DRAM clocks
®
Intel 82845 MCH for SDR Datasheet
55
Register Description
R
3.5.18
DRC—DRAM Controller Mode Register (Device 0)
Offset:
Default:
Access:
Size:
7C–7Fh
00000000h
R/W, RO
32 bits
Bit
Description
31:30
Revision Number (REV)—R/W. Reflects the revision number of the format used for SDRAM
register definition. Currently, this field must be 00, since this revision (rev 00) is the only existing
version of the specification.
29
Initialization Complete (IC)—R/W. This bit is used for communication of software state
between the memory controller and the BIOS. BIOS sets this bit to 1 after initialization of the
DRAM memory array is complete.
28
Dynamic Powerdown Mode Enable—R/W. When set, the system memory controller will put a
pair of rows into powerdown mode when all banks are pre-charged (closed). Once a bank is
accessed, the relevant pair of rows is taken out of powerdown mode.
The entry into powerdown mode is performed by de-activation of CKE. The exit is performed by
activation of CKE.
0 = Disable. System memory powerdown disabled
1 = Enable. System memory powerdown enabled
Note: Dynamic powerdown is a mobile only feature and not supported on desktop applications.
27:24
Active SDRAM Rows—R/W. Implementations may use this field to limit the maximum number
of SDRAM rows that may be active at once.
0000 = All rows allowed to be in the active state
Others = Reserved.
23:22
Reserved.
21:20
DRAM Data Integrity Mode (DDIM)—R/W. These bits select the system memory data integrity
mode.
00 = Non-ECC mode
10 = Error checking with correction
Other = Reserved
19:11
Reserved.
10:8
Refresh Mode Select (RMS)—R/W. This field determines whether refresh is enabled and, if
so, at what rate refreshes will be executed.
000 = Reserved
001 = Refresh enabled. Refresh interval 15.6 us
010 = Refresh enabled. Refresh interval 7.8 us
011 = Refresh enabled. Refresh interval 64 us
111 = Refresh enabled. Refresh interval 64 clocks (fast refresh mode)
Other = Reserved
7
56
Reserved.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
Bit
6:4
Description
Mode Select (SMS)—R/W. These bits select the special operational mode of the system
memory interface. The special modes are intended for initialization at power up.
000 = Post Reset state. When the MCH exits reset (power-up or otherwise), the mode select
field is cleared to “000”.
During any reset sequence, while power is applied and reset is active, the MCH asserts
all CKE signals. After internal reset is deasserted, CKE signals remain deasserted until
this field is written to a value different than “000”. On this event, all CKE signals are
asserted.
During suspend, MCH internal signal triggers system memory controller to flush pending
commands and enter all rows into Self-Refresh mode. As part of resume sequence, the
MCH will be reset ( which will clear this bit field to “000” and maintain CKE signals
deasserted). After internal reset is deasserted, CKE signals remain deasserted until this
field is written to a value different than “000”. On this event, all CKE signals are asserted.
During entry to other low power states (C3, S1), MCH internal signal triggers DRAM
controller to flush pending commands and enter all rows into Self-Refresh mode. During
exit to normal mode, MCH signal triggers DRAM controller to exit Self-Refresh and
resume normal operation without S/W involvement.
001 = NOP Command Enable. All processor cycles to system memory result in a NOP
command on the system memory interface.
010 = All Banks Pre-charge Enable. All processor cycles to system memory result in an “all
banks precharge” command on the system memory interface.
011 = Mode Register Set Enable. All processor cycles to system memory result in a “mode
register” set command on the system memory interface. Host address lines are mapped
to memory address lines to specify the command sent. Host address lines [15:3] are
mapped to SMA[12:0].
100 = Reserved
101 = Reserved
110 = CBR Refresh Enable. In this mode all processor cycles to system memory result in a
CBR cycle on the SDRAM interface
111 = Normal operation.
3:2
Reserved.
1:0
DRAM Type (DT)—RO. Used to select between supported SDRAM types.
00 = Single Data Rate (SDR) SDRAM.
01–11 = Reserved
®
Intel 82845 MCH for SDR Datasheet
57
Register Description
R
3.5.19
DERRSYN—DRAM Error Syndrome Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
86h
00h
RO
8 bits
This register is used to report the ECC syndromes for each quadword of a 32 byte-aligned data
quantity read from the system memory array.
Bit
7:0
Description
DRAM ECC Syndrome (DECCSYN). After a system memory ECC error, hardware loads this
field with a syndrome that describes the set of bits found to be in error.
Note: This field is locked from the time that it is loaded up to the time when the error flag is
cleared by software. If the first error was a single bit, correctable error, then a subsequent
multiple bit error will overwrite this field. In all other cases, an error that occurs after the
first error and before the error flag has been cleared by software will escape recording.
3.5.20
EAP—Error Address Pointer Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
8C–8Fh
0000_0000h
RO
32 bits
This register contains the address of the 32 byte-aligned data unit on which system memory ECC
error(s) was detected.
Bit
Descriptions
31:30
Reserved.
29:1
Error Address Pointer (EAP). This field is used to store address bits A[33:5] of the 32-bytealigned data unit of system memory of which an error (single bit or multi-bit error) has occurred.
Note: The value of this bit field represents the address of the first single or the first multiple bit
error occurrence after the error flag bits in the ERRSTS register have been cleared by
software. A multiple bit error will overwrite a single bit error. Once the error flag bits are set
as a result of an error, this bit field is locked and does not change as a result of a new error
until the error flag is cleared by software.
0
58
Reserved.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.21
PAM[0:6]—Programmable Attribute Map Registers
(Device 0)
Address Offset:
Default Value:
Attribute:
Size:
90–96h (PAM0–PAM6)
00h
R/W, RO
8 bits
The MCH allows programmable memory attributes on 13 Legacy memory segments of various
sizes in the 640 Kbytes to 1 Mbytes address range. Seven Programmable Attribute Map (PAM)
Registers are used to support these features. Cacheability of these areas is controlled via the
MTRR registers in the processor. Two bits are used to specify memory attributes for each memory
segment. These bits apply to host initiator only access to the PAM areas. The MCH forwards to
system memory for any AGP, PCI or hub interface-initiated accesses to the PAM areas. These
attributes are:
RE -
Read Enable. When RE = 1, the host read accesses to the corresponding memory
segment are claimed by the MCH and directed to system memory. Conversely, when
RE = 0, the host read accesses are directed to PCI0.
WE -
Write Enable. When WE = 1, the host write accesses to the corresponding memory
segment are claimed by the MCH and directed to system memory. Conversely, when
WE = 0, the host write accesses are directed to PCI0.
The RE and WE attributes permit a memory segment to be Read Only, Write Only, Read/Write, or
disabled. For example, if a memory segment has RE = 1 and WE = 0, the segment is Read Only.
Each PAM Register controls two regions, typically 16 KB in size. Each of these regions has a 4-bit
field. The four bits that control each region have the same encoding and defined in the following
table.
®
Bits [7, 3]
Reserved
Bits [6, 2]
Reserved
Bits [5, 1]
WE
Bits [4, 0]
RE
Description
X
X
0
0
Disabled. System memory is disabled and all
accesses are directed to the hub interface. The MCH
does not respond as a PCI target for any read or write
access to this area.
X
X
0
1
Read Only. Reads are forwarded to system memory
and writes are forwarded to the hub interface for
termination. This write protects the corresponding
memory segment. The MCH responds as an AGP or
hub interface target for read accesses but not for any
write accesses.
X
X
1
0
Write Only. Writes are forwarded to system memory
and reads are forwarded to the hub interface for
termination. The MCH responds as an AGP or hub
interface target for write accesses but not for any read
accesses.
X
X
1
1
Read/Write. This is the normal operating mode of
system memory. Both read and write cycles from the
host are claimed by the MCH and forwarded to
system memory. The MCH responds as an AGP or
hub interface target for both read and write accesses.
Intel 82845 MCH for SDR Datasheet
59
Register Description
R
At the time that a hub interface or AGP accesses to the PAM region may occur, the targeted PAM
segment must be programmed to be both readable and writeable.
As an example, consider BIOS that is implemented on the expansion bus. During the initialization
process, the BIOS can be shadowed in system memory to increase the system performance. When
BIOS is shadowed in system memory, it should be copied to the same address location. To shadow
the BIOS, the attributes for that address range should be set to write only. BIOS is shadowed by
first performing a read of that address. This read is forwarded to the expansion bus. The host then
does a write of the same address, which is directed to system memory. After the BIOS is
shadowed, the attributes for that memory area are set to read only so that all writes are forwarded
to the expansion bus. Table 9 and Figure 2 show the PAM registers and the associated attribute
bits:
Figure 2. PAM Register Attributes
Offset
PAM6
PAM5
PAM4
PAM3
PAM2
PAM1
PAM0
96h
95h
94h
93h
92h
91h
90h
7
6
5
4
3
2
1
0
R
R
WE
RE
R
R
WE
RE
Read Enable (R/W)
1=Enable
0=Disable
Reserved
Reserved
Write Enable (R/W)
1=Enable
0=Disable
Read Enable (R/W)
1=Enable
0=Disable
Write Enable (R/W)
1=Enable
0=Disable
Reserved
Reserved
pam
60
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
Table 9. PAM Register Attributes
PAM Reg
Attribute Bits
PAM0[3:0]
Memory Segment
Comments
Reserved
Offset
90h
PAM0[7:4]
R
R
WE
RE
0F0000h–0FFFFFh
BIOS Area
90h
PAM1[3:0]
R
R
WE
RE
0C0000h–0C3FFFh
ISA Add-on BIOS
91h
PAM1[7:4]
R
R
WE
RE
0C4000h–0C7FFFh
ISA Add-on BIOS
91h
PAM2[3:0]
R
R
WE
RE
0C8000h–0CBFFFh
ISA Add-on BIOS
92h
PAM2[7:4]
R
R
WE
RE
0CC000h–0CFFFFh
ISA Add-on BIOS
92h
PAM3[3:0]
R
R
WE
RE
0D0000h–0D3FFFh
ISA Add-on BIOS
93h
PAM3[7:4]
R
R
WE
RE
0D4000h–0D7FFFh
ISA Add-on BIOS
93h
PAM4[3:0]
R
R
RE
0D8000h–0DBFFFh
ISA Add-on BIOS
94h
PAM4[7:4]
R
R
WE
RE
0DC000h–0DFFFFh
ISA Add-on BIOS
94h
PAM5[3:0]
R
R
WE
RE
0E0000h–0E3FFFh
BIOS Extension
95h
PAM5[7:4]
R
R
WE
RE
0E4000h–0E7FFFh
BIOS Extension
95h
PAM6[3:0]
R
R
WE
RE
0E8000h–0EBFFFh
BIOS Extension
96h
PAM6[7:4]
R
R
WE
RE
0EC000h–0EFFFFh
BIOS Extension
96h
For details on overall system address mapping scheme see Chapter 4.
DOS Application Area (00000h–9FFFh)
The DOS area is 640 KB in size and it is further divided into two parts. The 512 KB area at
0h to 7FFFFh is always mapped to the system memory controlled by the MCH, while the 128 KB
address range from 080000 to 09FFFFh can be mapped to PCI0 or to system memory. By default
this range is mapped to system memory and can be declared as a system memory hole (accesses
forwarded to PCI0) via MCH FDHC configuration register.
Video Buffer Area (A0000h–BFFFFh)
Attribute bits do not control this 128 KB area. The host -initiated cycles in this region are always
forwarded to either PCI0 or AGP unless this range is accessed in SMM mode. Routing of
accesses is controlled by the Legacy VGA control mechanism of the “virtual” PCI-PCI
bridge device embedded within the MCH.
This area can be programmed as SMM area via the SMRAM register. When used as a SMM
space, this range cannot be accessed from the hub interface or AGP.
Expansion Area (C0000h–DFFFFh)
This 128 KB area is divided into eight 16 KB segments, which can be assigned with different
attributes via PAM control register as defined by the table above.
®
Intel 82845 MCH for SDR Datasheet
61
Register Description
R
Extended System BIOS Area (E0000h–EFFFFh)
This 64 KB area is divided into four 16 KB segments that can be assigned with different attributes
via PAM control register as defined by the table above.
System BIOS Area (F0000h–FFFFFh)
This area is a single 64 KB segment, which can be assigned with different attributes via PAM
control register as defined by the table above.
3.5.22
FDHC—Fixed DRAM Hole Control Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
97h
00h
R/W
8 bits
This 8-bit register controls a fixed DRAM hole: 15–16 MB.
Bit
7
Description
Hole Enable (HEN). This bit enables a memory hole in DRAM space. Host cycles matching an
enabled hole are passed on to the ICH2 through the hub interface. The hub interface cycles
matching an enabled hole will be ignored by the MCH. Note that a selected hole is not remapped.
0 = Disabled. No hole
1 = 15 MB–16 MB (1 MB hole)
6:0
62
Reserved.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.23
SMRAM—System Management RAM Control Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
9Dh
02h
R/W, RO, R/W/L
8 bits
The SMRAMC register controls how accesses to Compatible and Extended SMRAM spaces are
treated. The Open, Close, and Lock bits function only when the G_SMRAME bit is set to a 1.
Also, the OPEN bit must be reset before the LOCK bit is set.
Bit
Description
7
Reserved.
6
SMM Space Open (D_OPEN)—R/W/L. When D_OPEN=1 and D_LCK=0, the SMM space
DRAM is made visible even when SMM decode is not active. This is intended to help BIOS
initialize SMM space. Software should ensure that D_OPEN=1 and D_CLS=1 are not set at the
same time. When D_LCK is set to a 1, D_OPEN is reset to 0 and becomes read only.
5
SMM Space Closed (D_CLS)—R/W. When D_CLS = 1, SMM space DRAM is not accessible
to data references, even if SMM decode is active. Code references may still access SMM
space DRAM. This allows SMM software to reference “through” SMM space to update the
display, even when SMM is mapped over the VGA range. Software should ensure that
D_OPEN=1 and D_CLS=1 are not set at the same time.
Note that the D_CLS bit only applies to Compatible SMM space.
4
SMM Space Locked (D_LCK)—R/W. When D_LCK is set to 1, D_OPEN is reset to 0 and
D_LCK, D_OPEN, C_BASE_SEG, H_SMRAM_EN, TSEG_SZ and TSEG_EN become “Read
Only”. D_LCK can be set to 1 via a normal configuration space write but can only be cleared by
a Full Reset. The combination of D_LCK and D_OPEN provide convenience with security. The
BIOS can use the D_OPEN function to initialize SMM space and then use D_LCK to “lock
down” SMM space in the future so that no application software (or BIOS itself) can violate the
integrity of SMM space, even if the program has knowledge of the D_OPEN function.
3
Global SMRAM Enable (G_SMRAME)—R/W/L.
0 =Disable
1 =Enable. Compatible SMRAM functions are enabled, providing 128 KB of DRAM accessible
at the A0000h address while in SMM (ADS# with SMM decode). To enable Extended
SMRAM function this bit has to be set to 1.
Once D_LCK is set, this bit becomes read only.
2:0
Compatible SMM Space Base Segment (C_BASE_SEG)—RO. This field indicates the
location of SMM space. “SMM DRAM” is not remapped. It is simply “made visible” if the
conditions are right to access SMM space, otherwise the access is forwarded to the hub
interface.
010 = Hardwired to 010 to indicate that the MCH supports the SMM space at A0000h–BFFFFh.
®
Intel 82845 MCH for SDR Datasheet
63
Register Description
R
3.5.24
ESMRAMC—Extended System Mgmt RAM Control Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
9Eh
38h
RO, R/W, R/WC, R/W/L
8 bits
The Extended SMRAM register controls the configuration of Extended SMRAM space. The
Extended SMRAM (E_SMRAM) memory provides a write-back cacheable SMRAM memory
space that is above 1 MB.
Bit
Description
7
H_SMRAM_EN (H_SMRAME)—R/W/L. Controls the SMM memory space location (i.e., above 1
MB or below 1 MB). When G_SMRAME is 1 and H_SMRAME this bit is set to 1, the high
SMRAM memory space is enabled. SMRAM accesses from FEDA_0000h to FEDB_FFFFh are
remapped to DRAM address 000A0000h to 000BFFFFh.
Once D_LCK is set, this bit becomes read only.
6
E_SMRAM_ERR (E_SMERR)—R/WC.
0 = The software must write a 1 to this bit to clear it.
1 = This bit is set when host accesses the defined memory ranges in Extended SMRAM (High
Memory and T-segment) while not in SMM space and with the D-OPEN bit = 0.
5
SMRAM_Cache (SM_CACHE)—RO. Hardwired to 1.
4
SMRAM_L1_EN (SM_L1)—RO. Hardwired to 1.
3
SMRAM_L2_EN (SM_L2)—RO. Hardwired to 1.
2:1
TSEG_SZ[1-0] (T_SZ)—R/W. Selects the size of the TSEG memory block if enabled. This
memory is taken from the top of system memory space (i.e., TOM – TSEG_SZ), which is no
longer claimed by the memory controller (all accesses to this space are sent to the hub interface
if TSEG_EN is set). This field decodes as follows:
00 = (TOM–128 KB) to TOM
01 = (TOM–256 KB) to TOM
10 = (TOM–512 KB) to TOM
11 = (TOM–1 MB) to TOM
Once D_LCK is set, this bit becomes read only.
0
TSEG_EN (T_EN)—R/W/L. Enabling of SMRAM memory (TSEG, 128 KB, 256 KB, 512 KB or
1 MB of additional SMRAM memory) for Extended SMRAM space only. When G_SMRAME =1
and TSEG_EN = 1, the TSEG is enabled to appear in the appropriate physical address space.
Once D_LCK is set, this bit becomes read only.
64
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.25
ACAPID—AGP Capability Identifier Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
A0–A3h
0020_0002h
RO
32 bits
This register provides standard identifier for AGP capability.
Bit
Description
31:24
Reserved.
23:20
Major AGP Revision Number (MAJREV). These bits provide a major revision number of AGP
specification that this version of the MCH conforms. This field is hardwired to value of “0010b”
(i.e., implying Rev 2.x).
19:16
Minor AGP Revision Number (MINREV). These bits provide a minor revision number of AGP
specification that this version of the MCH conforms. This number is hardwired to value of “0000”
(i.e., implying Rev x.0)
Together with the major revision number this field identifies MCH as an AGP Revision 2.0
compliant device.
®
15:8
Next Capability Pointer (NCAPTR). AGP capability is the first and the last capability described
via the capability pointer mechanism; therefore, these bits are hardwired to 0h to indicate the
end of the capability linked list.
7:0
AGP Capability ID (CAPID). This field identifies the linked list item as containing AGP
registers. This field has a value of 0000_0010b assigned by the PCI SIG.
Intel 82845 MCH for SDR Datasheet
65
Register Description
R
3.5.26
AGPSTAT—AGP Status Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
A4–A7h
1F00_0217h
RO
32 bits
This register reports AGP device capability/status.
Bit
31:24
Description
Request Queue (RQ). This field contains the maximum number of AGP command requests the
MCH is configured to manage.
1Fh = Allows a maximum of 32 outstanding AGP command requests.
23:10
9
8:6
Reserved.
Side Band Addressing Support (SBA). Hardwired to 1 to indicate that the MCH supports side
band addressing.
Reserved.
5
Greater that 4 GB Support (4G). Hardwired to 0 to indicate that the MCH does not support
addresses greater than 4.
4
Fast Write Support (FW). Hardwired to 1 to indicate that the MCH supports Fast Writes from the
host to the AGP master.
3
Reserved.
2:0
Data Rate Support (RATE). Hardwired to 111. After reset, the MCH reports its data transfer rate
capability. Bit 0 identifies if AGP device supports 1x data transfer mode, bit 1 identifies if AGP
device supports 2x data transfer mode, bit 2 identifies if AGP device supports 4x data transfer
mode.
111 = 1x, 2x, and 4x data transfer modes are supported by the MCH
Note: The selected data transfer mode applies to both AD bus and SBA bus. It also applies to
Fast Writes if they are enabled.
66
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.27
AGPCMD—AGP Command Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
A8–ABh
0000_0000h
R/W
32 bits
This register provides control of the AGP operational parameters.
Bit
31:10
9
Description
Reserved.
SideBand Address Enable (SBAEN).
0 = Disable.
1 = Enable.
8
AGP Enable (AGPEN).
0 = The MCH ignores all AGP operations, including the sync cycle. Any AGP operation received
while this bit is 1 will be serviced, even if this bit is set to 0. If this bit transitions from a 1 to a 0
on a clock edge in the middle of an SBA command being delivered in 1X mode, the command
will be issued.
1 = The MCH will respond to AGP operations delivered via PIPE# or to operations delivered via
SBA if the AGP Side Band Enable bit is also set to 1.
7:5
4
Reserved.
Fast Write Enable (FWEN).
0 = When this bit is set to 0, or when the data rate bits are set to 1x mode, the memory write
transactions from the MCH to the AGP master use standard PCI protocol.
1 = MCH uses the Fast Write protocol for memory write transactions from the MCH to the AGP
master. Fast Writes occur at the data transfer rate selected by the DRATE bits (2:0) in this
register.
3
2:0
Reserved.
Data Rate (DRATE). The settings of these bits determine the AGP data transfer rate. One (and
only one) bit in this field must be set to indicate the desired data transfer rate.
001 = 1x transfer mode
010 = 2x transfer mode
100 = 4x transfer mode
Configuration software updates this field by setting only one bit that corresponds to the capability
of AGP master (after that capability has been verified by accessing the same functional register
in the AGP masters’ configuration space.)
Note: This field applies to AD and SBA buses. It also applies to Fast Writes if they are enabled.
®
Intel 82845 MCH for SDR Datasheet
67
Register Description
R
3.5.28
AGPCTRL—AGP Control Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
B0–B3h
0000_0000h
R/W
32 bits
This register provides for additional control of the AGP interface.
Bit
31:8
7
Description
Reserved.
GTLB Enable (GTLBEN). This bit provides enable and flush control of the GTLB.
0 =Disable (Default). GTLB is flushed by clearing the valid bits associated with each entry.
1 =Enable. Normal operations of the Graphics Translation Lookaside Buffer.
6:1
0
Reserved.
Data Rate 4x Override.
1 =The RATE[2:0] bit in the AGPSTS register will be read as a 001. This bit allows the BIOS to
force 1x mode. Note that this bit must be set by the BIOS before AGP configuration.
68
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.29
APSIZE—Aperture Size (Device 0)
Address Offset:
Default Value:
Access:
Size:
B4h
00h
R/W
8 bits
This register determines the effective size of the Graphics Aperture used for a particular MCH
configuration. This register can be updated by the MCH specific BIOS configuration sequence
before the PCI standard bus enumeration sequence takes place. If the register is not updated, the
default value will select an aperture of maximum size (i.e., 256 MB). The size of the table that will
correspond to a 256 MB aperture is not practical for most applications; therefore, these bits must
be programmed to a smaller practical value that will force adequate address range to be requested
via APBASE register from the PCI configuration software.
Bit
Description
7:6
Reserved.
5:0
Graphics Aperture Size (APSIZE). Each bit in APSIZE[5:0] operates on similarly ordered bits in
APBASE[27:22] of the Aperture Base configuration register. When a particular bit of this field is 0,
it forces the similarly ordered bit in APBASE[27:22] to behave as “hardwired” to 0. When a
particular bit of this field is set to 1, it allows corresponding bit of the APBASE[27:22] to be
read/write accessible. Only the following combinations are allowed:
5
4 3 2 1 0
Aperture Size
1
1 1 1 1 1
4 MB
1
1 1 1 1 0
8 MB
1
1 1 1 0 0
16 MB
1
1 1 0 0 0
32 MB
1
1 0 0 0 0
64 MB
1
0 0 0 0 0
128 MB
0
0 0 0 0 0
256 MB
Default for APSIZE[5:0]=000000b forces default APBASE[27:22] =000000b (i.e., all bits respond
as “hardwired” to 0). This provides maximum aperture size of 256 MB. As another example,
programming APSIZE[5:0]=111000b hardwires APBASE[24:22]=000b and while enabling
APBASE[27:25] as read/write.
®
Intel 82845 MCH for SDR Datasheet
69
Register Description
R
3.5.30
ATTBASE—Aperture Translation Table Base Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
B8–BBh
0000_0000h
R/W
32 bits
This register provides the starting address of the Graphics Aperture Translation Table Base
located in the system memory. This value is used by the MCH Graphics Aperture address
translation logic (including the GTLB logic) to obtain the appropriate address translation entry
required during the translation of the aperture address into a corresponding physical system
memory address. The ATTBASE register may be dynamically changed.
Note: The address provided via ATTBASE is 4 KB aligned.
Bit
31:12
Description
Aperture Translation Table Base (TTABLE). This field contains a pointer to the base of the
translation table used to map memory space addresses in the aperture range to addresses in
system memory.
Note: It should be modified only when the GTLB has been disabled.
11:0
70
Reserved.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.31
AMTT—AGP Interface Multi-Transaction Timer Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
BCh
00h
R/W
8 bits
AMTT is an 8-bit register that controls the amount of time that the MCH arbiter allows AGP
master to perform multiple back-to-back transactions. The MCH AMTT mechanism is used to
optimize the performance of the AGP master (using PCI protocol) that performs multiple back-toback transactions to fragmented memory ranges (and as a consequence it can not use long burst
transfers). The AMTT mechanism applies to the host-AGP transactions as well and it guarantees
to the processor a fair share of the AGP interface bandwidth.
The number of clocks programmed in the AMTT represents the guaranteed time slice (measured in
66 MHz clocks) allotted to the current agent (either AGP master or host bridge) after which the
AGP arbiter will grant the bus to another agent. The default value of AMTT is 00h and disables
this function. The AMTT value can be programmed with 8-clock granularity. For example, if the
AMTT is programmed to 18h, then the selected value corresponds to the time period of 24 AGP
(66 MHz) clocks.
Bit
®
Description
7:3
Multi-Transaction Timer Count Value (MTTC). The number programmed in these bits
represents the guaranteed time slice (measured in eight 66 MHz clock granularity) allotted to
the current agent (either AGP master or MCH) after which the AGP arbiter will grant the bus to
another agent.
2:0
Reserved.
Intel 82845 MCH for SDR Datasheet
71
Register Description
R
3.5.32
LPTT—AGP Low Priority Transaction Timer Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
BDh
00h
R/W
8 bits
LPTT is an 8-bit register similar in function to AMTT. This register is used to control the
minimum tenure on the AGP for low-priority data transactions (both reads and writes) issued using
PIPE# or SB mechanisms.
The number of clocks programmed in the LPTT represents the guaranteed time slice (measured in
66 MHz clocks) allotted to the current low priority AGP transaction data transfer state. This does
not necessarily apply to a single transaction but it can span over multiple low-priority transactions
of the same type. After this time expires, the AGP arbiter may grant the bus to another agent if
there is a pending request. The LPTT does not apply in the case of high-priority request where
ownership is transferred directly to high-priority requesting queue. The default value of LPTT is
00h and disables this function. The LPTT value can be programmed with 8-clock granularity. For
example, if the LPTT is programmed to 10h, the selected value corresponds to the time period of
16 AGP (66 MHz) clocks.
72
Bit
Description
7:3
Low Priority Transaction Timer Count Value (LPTTC). The number of clocks programmed in
these bits represents the guaranteed time slice (measured in eight 66 MHz clock granularity)
allotted to the current low priority AGP transaction data transfer state.
2:0
Reserved.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.33
TOM—Top of Low Memory Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
C4–C5h
0100h
R/W
16 bits
This register contains the maximum address below 4 GB that should be treated as a memory
access. Note that this register must be set to a value of 0100h (16 MB) or greater. Usually it will
sit below the areas configured for the hub interface, PCI memory, and the graphics aperture.
Bit
15:4
Description
Top of Low Memory (TOM). This register contains the address that corresponds to bits 31 to
20 of the maximum system memory address that lies below 4 GB. Configuration software
should set this value to either the maximum amount of memory in the system or to the
minimum address allocated for PCI memory or the graphics aperture, whichever is smaller.
Programming Example: 400h = 1 GB. An access to 4000_0000h or above will be considered
above the TOM and therefore not routed to system memory. It may go to AGP, aperture, or
subtractively decode to the hub interface.
3:0
®
Reserved.
Intel 82845 MCH for SDR Datasheet
73
Register Description
R
3.5.34
MCHCFG—MCH Configuration Register (Device 0)
Offset:
Default:
Access:
Size:
C6–C7h
0000h
R/W, RO
16 bits
Bit
15:12
11
Description
Reserved.
System Memory Frequency Select. This bit must be programmed prior to memory
initialization.
0 = Reserved
1 = System Memory frequency is set to 133 MHz
11:6
5
Reserved.
MDA Present (MDAP)—R/W. This bit works with the VGA Enable bit in the BCTRL1 register
(device 1) to control the routing of host-initiated transactions targeting MDA compatible I/O and
memory address ranges. This bit should not be set when the VGA Enable bit is not set in either
device 1. If the VGA enable bit is set, then accesses to I/O address range x3BCh–x3BFh are
forwarded to the hub interface. MDA resources are defined as the following:
Memory:
0B0000h–0B7FFFh
I/O:
3B4h, 3B5h, 3B8h, 3B9h, 3BAh, 3BFh,
(including ISA address aliases, A[15:10] are not used in decode)
Any I/O reference that includes the I/O locations listed above, or their aliases, are forwarded to
the hub interface, even if the reference includes I/O locations not listed above.
Refer to the Chapter 4 for further information.
4:3
2
Reserved.
In-Order Queue Depth (IOQD)–RO. This bit reflects the value sampled on HA7# on the
deassertion of the CPURST#. It indicates the depth of the host bus in-order queue (i.e., level of
host bus pipelining).
0 = HA7# was sampled asserted (i.e., 0); the depth of the host bus in-order queue is set to 1
(i.e., no pipelining support on the host bus).
1 = HA7# was sampled 1 (i.e., undriven on the host bus); the depth of the host bus in-order
queue is configured to the maximum allowed by the host bus protocol (i.e., 12). Note that
the MCH has a 12 deep IOQ.
Note that HA7# is not driven by the MCH during CPURST#. If an IOQ size of 1 is desired, HA7#
must be driven low during CPURST# by an external source.
1
APIC Memory Range Disable (APICDIS)—R/W.
0 = The MCH sends cycles between 0_FEC0_0000 and 0_FEC7_FFFF to the hub interface.
1 = The MCH forwards accesses to the IOAPIC regions to the appropriate interface, as
specified by the memory and PCI configuration registers.
0
74
Reserved.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.35
ERRSTS—Error Status Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
C8–C9h
0000h
R/WC
16 bits
This register is used to report various error conditions via the hub interface messages to ICH2. An
SERR, SMI, or SCI error message may be generated via the hub interface on a zero to one
transition of any of these flags when enabled in the PCICMD/ERRCMD, SMICMD, or SCICMD
registers, respectively. These bits are set, regardless of whether or not the SERR is enabled and
generated.
Bit
15:10
9
Description
Reserved.
LOCK to non-DRAM Memory Flag (LCKF).
0 =Software must write a 1 to clear this status bit.
1 =Indicates that a host initiated LOCK cycle targeting non-DRAM memory space occurred.
8:7
6
Reserved.
SERR on Hub Interface Target Abort (TAHLA).
0 =Software must write a 1 to clear this status bit.
1 =MCH detected that a MCH-originated hub interface cycle was terminated with a Target Abort
completion packet or special cycle.
5
MCH Detects Unimplemented Hub Interface Special Cycle (HIAUSC).
0 =Software must write a 1 to clear this status bit.
1 =MCH detected an Unimplemented Special Cycle on the hub interface.
4
AGP Access Outside of Graphics Aperture Flag (OOGF).
0 =Software must write a 1 to clear this status bit.
1 =Indicates that an AGP access occurred to an address that is outside of the graphics aperture
range.
3
Invalid AGP Access Flag (IAAF).
0 =Software must write a 1 to clear this status bit.
1 =Indicates that an AGP access was attempted outside of the graphics aperture and either to
the 640 KB – 1 MB range or above the top of memory.
2
Invalid Graphics Aperture Translation Table Entry (ITTEF).
0 =Software must write a 1 to clear this status bit.
1 =Indicates that an invalid translation table entry was returned in response to an AGP access
to the graphics aperture.
1
Multiple-bit DRAM ECC Error Flag (DMERR).
0 =After software completes the error processing, a value of 1 is written to this bit field to set the
value back to 0 and unlock the error logging mechanism.
1 =A memory read data transfer had an uncorrectable multiple-bit error. When this bit is set, the
address and device number that caused the error are logged in the EAP Register. Software
uses bits [1:0] to detect whether the logged error address is for Single or Multiple-bit error.
®
Intel 82845 MCH for SDR Datasheet
75
Register Description
R
Bit
0
Description
Single-bit DRAM ECC Error Flag (DSERR).
0 =Software must write a 1 to clear this bit and unlock the error logging mechanism.
1 =A memory read data transfer had a single-bit correctable error and the corrected data was
sent for the access. When this bit is set, the address, channel number, and device number
that caused the error are logged in the EAP Register. When this bit is set, the EAP, CN, DN,
and ES fields are locked to further single bit error updates until the processor clears this bit
by writing a 1.
3.5.36
ERRCMD—Error Command Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
CA–CBh
0000h
R/W
16 bits
This register enables various errors to generate a SERR message via the hub interface. Since the
MCH does not have an SERR# signal, SERR messages are passed from the MCH to the ICH2
over the hub interface. When a bit in this register is set, a SERR message will be generated on the
hub interface when the corresponding flag is set in the ERRSTS register. The actual generation of
the SERR message is globally enabled for Device 0 via the PCICMD register.
Note: An error can generate one and only one error message via the hub interface. It is software’s
responsibility to make sure that when an SERR error message is enabled for an error condition,
SMI and SCI error messages are disabled for that same error condition.
Bit
15:10
9
Description
Reserved.
SERR on Non-DRAM Lock (LCKERR).
0 = Disable.
1 = Enable. The MCH will generate a hub interface SERR special cycle when a processor lock
cycle is detected that does not hit system memory.
8:7
6
Reserved.
SERR on Target Abort on Hub Interface Exception (TAHLA_SERR).
0 = Disable.
1 = Enable. Generation of the hub interface SERR message is enabled when a MCH-originated
hub interface cycle is completed with “Target Abort” completion packet or special cycle
status.
5
SERR on Detecting Hub Interface Unimplemented Special Cycle (HIAUSCERR). SERR
messaging for Device 0 is globally enabled in the PCICMD register.
0 = Disable. MCH does not generate an SERR message for this event.
1 = Enable. MCH generates a SERR message over the hub interface when an unimplemented
Special Cycle is received on the hub interface.
76
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
Bit
4
Description
SERR on AGP Access Outside of Graphics Aperture (OOGF_SERR).
0 = Disable.
1 = Enable. Generation of the hub interface SERR message is enabled when an AGP access
occurs to an address outside of the graphics aperture.
3
SERR on Invalid AGP Access (IAAF_SERR).
0 = Disable.
1 = Generation of the hub interface SERR message is enabled when an AGP access occurs to
an address outside of the graphics aperture and either to the 640 KB – 1 MB range or above
the top of memory.
2
SERR on Invalid Translation Table Entry (ITTEF_SERR).
0 = Disable.
1 = Enable. Generation of the hub interface SERR message is enabled when an invalid
translation table entry was returned in response to an AGP access to the graphics aperture.
1
SERR Multiple-Bit DRAM ECC Error (DMERR_SERR).
0 = Disable. For systems not supporting ECC, this bit must be disabled.
1 = Enable. Generation of the hub interface SERR message is enabled when the MCH system
memory controller detects a multiple-bit error.
0
SERR on Single-bit ECC Error (DSERR).
0 = Disable. For systems that do not support ECC, this bit must be disabled.
1 = Enable. Generation of the hub interface SERR message is enabled when the MCH system
memory controller detects a single bit error.
®
Intel 82845 MCH for SDR Datasheet
77
Register Description
R
3.5.37
SMICMD—SMI Command Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
CC–CDh
0000h
R/W
16 bits
This register enables various errors to generate a SMI message via the hub interface.
Note: An error can generate one and only one error message via the hub interface. It is software’s
responsibility to make sure that when an SMI error message is enabled for an error condition,
SERR and SCI error messages are disabled for that same error condition.
Bit
15:2
1
Description
Reserved.
SMI on Multiple-Bit DRAM ECC Error (DMERR).
0 =Disable. For systems not supporting ECC, this bit must be disabled.
1 =Enable. Generation of the hub interface SMI message is enabled when the MCH system
memory controller detects a multiple-bit error.
0
SMI on Single-bit ECC Error (DSERR).
0 =Disable. For systems that do not support ECC, this bit must be disabled.
1 =Enable. Generation of the hub interface SMI message is enabled when the MCH system
memory controller detects a single bit error.
3.5.38
SCICMD—SCI Command Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
CE–CDh
0000h
R/W
16 bits
This register enables various errors to generate a SCI message via the hub interface.
Note: An error can generate one and only one error message via the hub interface. It is software’s
responsibility to make sure that when an SCI error message is enabled for an error condition, SERR
and SMI error messages are disabled for that same error condition.
Bit
15:2
1
Description
Reserved.
SCI on Multiple-Bit DRAM ECC Error (DMERR).
0 =Disable. For systems not supporting ECC, this bit must be disabled.
1 =Enable. Generation of the hub interface SCI message is enabled when the MCH system
memory controller detects a multiple-bit error.
0
SCI on Single-bit ECC Error (DSERR).
0 =Disable. For systems that do not support ECC, this bit must be disabled.
1 =Enable. Generation of the hub interface SCI message is enabled when the MCH system
memory controller detects a single bit error.
78
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.5.39
SKPD—Scratchpad Data Register (Device 0)
Address Offset:
Default Value:
Access:
Size:
DE–DFh
0000h
R/W
16 bits
Bit
15:0
3.5.40
Description
Scratchpad [15:0]. These bits are R/W storage bits that have no effect on the MCH
functionality.
CAPID—Product Specific Capability Identifier Register
(Device 0)
Address Offset:
Default Value:
Access:
Size:
Bit
31
E4h
0104A009h
RO
32 bits
Descriptions
System Memory Capability.
0 = Component only supports SDR SDRAM memory; DRAM Type field is read-only. (default)
1 = Reserved
30
Mobile Power Management Capability.
0 = Component is NOT capable of all mobile power management features and is limited to
desktop use only (default)
1 = Component is capable of all mobile power management features.
29:28
Reserved.
27:24
CAPID Version.
0001b = First revision of the CAPID register definition. (default)
23:16
CAPID Length.
04h = Indicates a structure length of 4 bytes. (default)
15:8
Next Capability Pointer.
A0h = Points to the next Capability ID in this device (ACAPID register). (default)
7:0
CAP_ID.
1001b = Identifies the CAP_ID assigned by the PCI SIG for vendor dependent capability
pointers. (default)
®
Intel 82845 MCH for SDR Datasheet
79
Register Description
R
3.6
Bridge Registers (Device 1)
Table 10. provides the register address map for Device 0 PCI configuration space. An “s” in the
Default Value column indicates that a strap determines the power-up default value for that bit.
®
Table 10. Intel MCH Configuration Space (Device 1)
80
Address
Offset
Symbol
Name
Default
00-01h
VID1
Vendor Identification
8086h
RO
02–03h
DID1
Device Identification
1A31h
RO
04–05h
PCICMD1
PCI Command
0000h
RO, R/W
06–07h
PCISTS1
PCI Status
00A0h
RO, R/WC
08
RID1
Revision Identification
03h, 04h
RO
09
—
Reserved
—
—
0Ah
SUBC1
Sub-Class Code
04h
RO
0Bh
BCC1
Base Class Code
06h
RO
0Ch
—
Reserved
—
—
0Dh
MLT1
Master Latency Timer
00h
R/W
0Eh
HDR1
Header Type
01h
RO
0F–17h
—
Reserved
—
—
18h
PBUSN1
Primary Bus Number
00h
RO
19h
SBUSN1
Secondary Bus Number
00h
R/W
1Ah
SUBUSN1
Subordinate Bus Number
00h
R/W
1Bh
SMLT1
Secondary Bus Master Latency Timer
00h
R/W
1Ch
IOBASE1
I/O Base Address
F0h
R/W
1Dh
IOLIMIT1
I/O Limit Address
00h
R/W
1E–1Fh
SSTS1
Secondary Status
02A0h
RO, R/WC
20–21h
MBASE1
Memory Base Address
FFF0h
R/W
22–23h
MLIMIT1
Memory Limit Address
0000h
R/W
24–25h
PMBASE1
Prefetchable Memory Base Address
FFF0h
R/W
26–27h
PMLIMIT1
Prefetchable Memory Limit Address
0000h
R/W
28–3Dh
—
Reserved
—
—
3Eh
BCTRL1
Bridge Control
00h
RO, R/W
3Fh
—
Reserved
—
—
40h
ERRCMD1
Error Command
00h
R/W
41–4Fh
—
Reserved
—
—
50–57h
DWTC
DRAM Write Thermal Management Control
0000000
0h
R/W/L
®
Access
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.6.1
Address
Offset
Symbol
58–5Fh
DRTC
59–FFh
—
Name
Default
Access
DRAM Read Thermal Management Control
0000000
0h
R/W/L
Reserved
—
—
VID1—Vendor Identification Register (Device 1)
Address Offset:
Default Value:
Attribute:
Size:
00–01h
8086h
RO
16 bits
The VID1 register contains the vendor identification number. This 16-bit register combined with
the DID1 Register uniquely identifies any PCI device. Writes to this register have no effect.
Bit
15:0
3.6.2
Description
Vendor Identification Number. This is a 16-bit value assigned to Intel. Intel VID = 8086h.
DID1—Device Identification Register (Device 1)
Address Offset:
Default Value:
Attribute:
Size:
02–03h
1A31h
RO
16 bits
This 16-bit register combined with the VID1 register uniquely identifies any PCI device. Writes to
this register have no effect.
Bit
15:0
®
Description
Device Identification Number. This is a 16-bit value assigned to the MCH Device 1.
MCH1 Device 1 DID = 1A31h.
Intel 82845 MCH for SDR Datasheet
81
Register Description
R
3.6.3
PCICMD1—PCI-PCI Command Register (Device 1)
Address Offset:
Default:
Access:
Size
04–05h
0000h
RO, R/W
16 bits
Bit
15:10
Descriptions
Reserved.
9
Fast Back-to-Back (FB2B)—RO. Not Implemented; Hardwired to 0.
8
SERR Message Enable (SERRE1)—R/W. This bit is a global enable bit for Device 1 SERR
messaging. The MCH does not have an SERR# signal. The MCH communicates the SERR#
condition by sending an SERR message to the ICH2.
0 = Disable. SERR message is not generated by the MCH for Device 1.
1 = Enable. MCH is enabled to generate SERR messages over the hub interface for specific
Device 1 error conditions that are individually enabled in the BCTRL register. The error
status is reported in the PCISTS1 register.
NOTE: This bit only controls SERR messaging for the Device 1. Device 0 has its own SERRE
bit to control error reporting for error conditions occurring on Device 0.
7
Address/Data Stepping (ADSTEP)—RO. Not Implemented; Hardwired to 0.
6
Parity Error Enable (PERRE1)—RO. Not Implemented; Hardwired to 0.
5
Reserved.
4
Memory Write and Invalidate Enable (MWIE)—RO. Not Implemented; Hardwired to 0.
3
Special Cycle Enable (SCE)—RO. Not Implemented; Hardwired to 0.
2
Bus Master Enable (BME1)—R/W. This bit is not functional. It is a R/W bit for compatibility
with compliance testing software.
1
Memory Access Enable (MAE1)—R/W.
0 = Disable. All of Device 1’s memory space is disabled.
1 = Enable. The Memory and Prefetchable memory address ranges defined in the MBASE1,
MLIMIT1, PMBASE1, and PMLIMIT1 registers are enabled.
0
I/O Access Enable (IOAE1)—R/W.
0 = Disable. All of device 1’s I/O space is disabled.
1 = Enable. This bit must be set to1 to enable the I/O address range defined in the IOBASE1,
and IOLIMIT1 registers.
82
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.6.4
PCISTS1—PCI-PCI Status Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
06–07h
00A0h
RO, R/WC
16 bits
PCISTS1 is a 16-bit status register that reports the occurrence of error conditions associated with
primary side of the “virtual” PCI-PCI bridge embedded n the MCH. Since this device does not
physically reside on PCI_A, it reports the optimum operating conditions so that it does not restrict
the capability of PCI_A.
Bit
Descriptions
15
Detected Parity Error (DPE1)—RO. Not Implemented; Hardwired to 0.
14
Signaled System Error (SSE1)—R/WC.
0 =Software clears this bit by writing a 1 to it.
1 =MCH device 1 generated an SERR message over the hub interface for any enabled Device
1 error condition. Device 1 error conditions are enabled in the ERRCMD, PCICMD1 and
BCTRL1 registers. Device 1 error flags are read/reset from the ERRSTS and SSTS1
register.
13
Received Master Abort Status (RMAS1)—RO. Not Implemented; Hardwired to 0.
12
Received Target Abort Status (RTAS1)—RO. Not Implemented; Hardwired to 0.
11
Signaled Target Abort Status (STAS1)—RO. Not Implemented; Hardwired to 0.
10:9
8
Data Parity Detected (DPD1). Not Implemented; Hardwired to 0.
7
Fast Back-to-Back (FB2B1)—RO. Hardwired to 1. The AGP port always supports fast back to
back transactions.
6
Reserved.
5
66 MHz Capability (CAP66)—RO. Hardwired to 1. Indicates that the AGP port is 66 MHz
capable.
4:0
®
DEVSEL# Timing (DEVT1)—RO. Hardwired to 00b. Indicate that the device 1 uses the fastest
possible decode.
Reserved.
Intel 82845 MCH for SDR Datasheet
83
Register Description
R
3.6.5
RID1—Revision Identification Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
08h
See RID1 table below
RO
8 bits
This register contains the revision number of the MCH device 1. These bits are read only and
writes to this register have no effect.
Bit
7:0
Description
Revision Identification Number (RID): This is an 8-bit value that indicates the revision
identification number for the MCH device 1.
03h = A3 Stepping
04h = B0 Stepping
3.6.6
SUBC1—Sub-Class Code Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
0Ah
04h
RO
8 bits
This register contains the Sub-Class Code for the MCH device 1.
Bit
7:0
Description
Sub-Class Code (SUBC1): This is an 8-bit value that indicates the category of bridge of the
MCH.
04h = Host bridge.
3.6.7
BCC1—Base Class Code Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
0Bh
06h
RO
8 bits
This register contains the Base Class Code of the MCH device 1.
Bit
7:0
Description
Base Class Code (BASEC): This is an 8-bit value that indicates the Base Class Code for the
MCH device 1.
06h = Bridge device.
84
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.6.8
MLT1—Master Latency Timer Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
0Dh
00h
R/W
8 bits
This functionality is not applicable. It is described here since these bits should be implemented as
a read/write to prevent standard PCI-PCI bridge configuration software from getting “confused”.
Bit
3.6.9
Description
7:3
Not applicable but supports read/write operations. (Reads return previously written data.)
2:0
Reserved.
HDR1—Header Type Register (Device 1)
Offset:
Default:
Access:
Size:
0Eh
01h
RO
8 bits
This register identifies the header layout of the configuration space.
Bit
7:0
3.6.10
Descriptions
This read only field always returns 01h when read. Writes have no effect.
PBUSN1—Primary Bus Number Register (Device 1)
Offset:
Default:
Access:
Size:
18h
00h
RO
8 bits
This register identifies that “virtual” PCI-PCI Bridge is connected to bus #0.
Bit
7:0
®
Descriptions
Bus Number. Hardwired to 0.
Intel 82845 MCH for SDR Datasheet
85
Register Description
R
3.6.11
SBUSN1—Secondary Bus Number Register (Device 1)
Offset:
Default:
Access:
Size:
19h
00h
R/W
8 bits
This register identifies the bus number assigned to the second bus side of the “virtual” PCI-PCI
bridge i.e. to AGP. This number is programmed by the PCI configuration software to allow
mapping of configuration cycles to AGP.
Bit
7:0
3.6.12
Descriptions
Bus Number. Programmable. Default = 00h.
SUBUSN1—Subordinate Bus Number Register (Device 1)
Offset:
Default:
Access:
Size:
1Ah
00h
R/W
8 bits
This register identifies the subordinate bus (if any) that resides at the level below AGP. This
number is programmed by the PCI configuration software to allow mapping of configuration
cycles to AGP.
Bit
7:0
86
Descriptions
Bus Number. Programmable. Default = 0.
®
Intel 82845 MCH for SDR Datasheet
Register Description
R
3.6.13
SMLT1—Secondary Master Latency Timer Register
(Device 1)
Address Offset:
Default Value:
Access:
Size:
1Bh
00h
R/W
8 bits
This register controls the bus tenure of the MCH on AGP. MLT is an 8-bit register that controls
the amount of time the MCH, as an AGP/PCI bus master, can burst data on the AGP bus. The
count value is an 8-bit quantity; however, MLT[2:0] are reserved and have a value of 0 when
determining the count value. The MCH’s MLT is used to guarantee to the AGP master a minimum
amount of the system resources. When the MCH begins the first AGP FRAME# cycle after being
granted the bus, the counter is loaded and enabled to count from the assertion of FRAME#. If the
count expires while the MCH’s grant is removed (due to AGP master request), the MCH will lose
the use of the bus, and the AGP master agent may be granted the bus. If the MCH’s bus grant is
not removed, the MCH continues to own the AGP bus, regardless of the MLT expiration or idle
condition. Note that the MCH always properly terminates an AGP transaction, with FRAME#
negation prior to the final data transfer.
The number of clocks programmed in the MLT represents the guaranteed time slice (measured in
66 MHz AGP clocks) allotted to the MCH, after which it must complete the current data transfer
phase and then surrender the bus as soon as its bus grant is removed. For example, if the MLT is
programmed to 18h, the value is 24 AGP clocks. The default value of MLT is 00h and disables
this function. When the MLT is disabled, the burst time for the MCH is unlimited (i.e., the MCH
can burst forever).
Bit
®
Description
7:3
Secondary MLT Counter Value. Default=0s (i.e., SMLT disabled)
2:0
Reserved.
Intel 82845 MCH for SDR Datasheet
87
Register Description
R
3.6.14
IOBASE1—I/O Base Address Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
1Ch
F0h
R/W
8 bits
This register controls the hosts to AGP I/O access routing based on the following formula:
IO_BASE ≤ address ≤ Ι O_LIMIT
Only upper 4 bits are programmable. For the purpose of address decode, address bits A[11:0] are
treated as 0. Thus, the bottom of the defined I/O address range is aligned to a 4 KB boundary.
Bit
3.6.15
Description
7:4
I/O Address Base. Corresponds to A[15:12] of the I/O address. (Default=F0h)
3:0
Reserved.
IOLIMIT1—I/O Limit Address Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
1Dh
00h
R/W
8 bits
This register controls the hosts to AGP I/O access routing based on the following formula:
IO_BASE ≤ address ≤ IO_LIMIT
Only upper 4 bits are programmable. For the purpose of address decode, address bits A[11:0] are
assumed to be FFFh. Thus, the top of the defined I/O address range is at the top of a 4 KB aligned
address block.
Bit
88
Description
7:4
I/O Address Limit. Corresponds to A[15:12] of the I/O address. (Default=0)
3:0
Reserved. (Only 16-bit addressing supported.)
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Intel 82845 MCH for SDR Datasheet
Register Description
R
3.6.16
SSTS1—Secondary PCI-PCI Status Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
1E–1Fh
02A0h
RO, R/WC
16 bits
SSTS1 is a 16-bit status register that reports the occurrence of error conditions associated with
secondary side (i.e., AGP side) of the “virtual” PCI-PCI bridge embedded in the MCH.
Bit
15
Descriptions
Detected Parity Error (DPE1)—R/WC.
0 = Software sets this bit to 0 by writing a 1 to it.
1 = MCH detected a parity error in the address or data phase of AGP bus transactions.
14
Reserved.
13
Received Master Abort Status (RMAS1)—R/WC.
0 = Software sets this bit to 0 by writing a 1 to it.
1 = MCH terminated a Host-to-AGP with an unexpected master abort.
12
Received Target Abort Status (RTAS1)—R/WC.
0 = Software sets this bit to 0 by writing a 1 to it.
1 = MCH-initiated transaction on AGP is terminated with a target abort.
11
Signaled Target Abort Status (STAS1)—RO. Hardwired to a 0. The MCH does not generate
target abort on AGP.
10:9
DEVSEL# Timing (DEVT1)—RO. Hardwired to 01. This 2-bit field indicates the timing of the
DEVSEL# signal when the MCH responds as a target on AGP. This field indicates the time
when a valid DEVSEL# can be sampled by the initiator of the PCI cycle.
01 = Medium timing.
8
Master Data Parity Error Detected (DPD1)—RO. Hardwired to 0. MCH does not implement
G_PERR# signal.
7
Fast Back-to-Back (FB2B1)—RO. Hardwired to 1. MCH as a target supports fast back-to-back
transactions on AGP.
6
Reserved.
5
66 MHz Capable (CAP66)—RO. Hardwired to 1. AGP bus is capable of 66 MHz operation.
4:0
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Reserved.
Intel 82845 MCH for SDR Datasheet
89
Register Description
R
3.6.17
MBASE1—Memory Base Address Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
20–21h
FFF0h
R/W
16 bits
This register controls the host to AGP non-prefetchable memory accesses routing based on the
following formula:
MEMORY_BASE1 ≤ address ≤ MEMORY_LIMIT1
The upper 12 bits of the register are read/write and correspond to the upper 12 address bits
A[31:20] of the 32-bit address. The bottom 4 bits of this register are read-only and return 0s when
read. The configuration software must initialize this register. For the purpose of address decode,
address bits A[19:0] are assumed to be 0. Thus, the bottom of the defined memory address range
will be aligned to a 1 MB boundary.
Bit
3.6.18
Description
15:4
Memory Address Base 1 (MEM_BASE1). Corresponds to A[31:20] of the memory address.
3:0
Reserved.
MLIMIT1—Memory Limit Address Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
22–23h
0000h
R/W
16 bits
This register controls the host to AGP non-prefetchable memory accesses routing based on the
following formula:
MEMORY_BASE1 ≤ address ≤ MEMORY_LIMIT1
The upper 12 bits of the register are read/write and correspond to the upper 12 address bits
A[31:20] of the 32-bit address. The bottom 4 bits of this register are read-only and return 0s when
read. The configuration software must initialize this register. For the purpose of address decode,
address bits A[19:0] are assumed to be FFFFFh. Thus, the top of the defined memory address
range will be at the top of a 1 MB aligned memory block.
Bit
Description
15:4
Memory Address Limit 1(MEM_LIMIT1). Corresponds to A[31:20] of the memory address.
Default=0
3:0
Reserved.
Note: Memory range covered by MBASE1 and MLIMIT1 registers are used to map non-prefetchable
AGP address ranges (typically, where control/status memory-mapped I/O data structures of the
graphics controller will reside) and PMBASE 1and PMLIMIT1 Registers are used to map
prefetchable address ranges (typically, graphics local memory). This segregation allows
application of USWC space attributes to be performed in a true plug-and-play manner to the
prefetchable address range for improved host-AGP memory access performance.
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Register Description
R
3.6.19
PMBASE1—Prefetchable Memory Base Address Register
(Device 1)
Address Offset:
Default Value:
Access:
Size:
24–25h
FFF0h
R/W
16 bits
This register controls the host to AGP prefetchable memory accesses routing based on the
following formula:
PREFETCHABLE_MEMORY_BASE1 ≤ address ≤ PREFETCHABLE_MEMORY_LIMIT1
The upper 12 bits of the register are read/write and correspond to the upper 12 address bits
A[31:20] of the 32-bit address. The bottom 4 bits of this register are read-only and return 0s when
read. The configuration software must initialize this register. For the purpose of address decode,
address bits A[19:0] are assumed to be 0. Thus, the bottom of the defined memory address range
will be aligned to a 1 MB boundary.
Bit
3.6.20
Description
15:4
Prefetchable Memory Address Base 1(PMEM_BASE1). Corresponds to A[31:20] of the
memory address.
3:0
Reserved.
PMLIMIT1—Prefetchable Memory Limit Address Register
(Device 1)
Address Offset:
Default Value:
Access:
Size:
26–27h
0000h
R/W
16 bits
This register controls the host to AGP prefetchable memory accesses routing based on the
following formula:
PREFETCHABLE_MEMORY_BASE1 ≤ address ≤ PREFETCHABLE_MEMORY_LIMIT1
The upper 12 bits of the register are read/write and correspond to the upper 12 address bits
A[31:20] of the 32-bit address. The bottom 4 bits of this register are read-only and return 0s when
read. The configuration software must initialize this register. For the purpose of address decode,
address bits A[19:0] are assumed to be FFFFFh. Thus, the top of the defined memory address
range will be at the top of a 1 MB aligned memory block.
Bit
Description
15:4
Prefetchable Memory Address Limit 1(PMEM_LIMIT1). Corresponds to A[31:20] of the
memory address. (Default=00h)
3:0
Reserved.
Note: Prefetchable memory range is supported to allow segregation by the configuration software
between the memory ranges that must be defined as UC and the ones that can be designated as a
USWC (i.e., prefetchable) from the processor perspective.
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91
Register Description
R
3.6.21
BCTRL1—PCI-PCI Bridge Control Register (Device 1)
Address Offset:
Default:
Access:
Size
3Eh
00h
RO, R/W
8 bits
This register provides extensions to the PCICMD1 register that are specific to PCI-PCI bridges.
BCTRL1 provides additional control for the secondary interface (i.e., AGP) as well as some bits
that affect the overall behavior of the “virtual” PCI-PCI bridge embedded in the MCH (e.g., VGA
compatible address ranges mapping).
Bit
Descriptions
7
Fast Back to Back Enable (FB2BEN)—RO. Hardwired to 0. Since there is only one target
allowed on AGP, this bit is meaningless. The MCH will not generate FB2B cycles in 1x mode, but
will generate FB2B cycles in 2x and 4x Fast Write modes.
6
Secondary Bus Reset (SRESET)—RO. Hardwired to 0. MCH does not support generation of
reset via this bit on the AGP.
Note: The only way to perform a hard reset of the AGP is via the system reset either initiated by
software or hardware via the ICH2.
5
Master Abort Mode (MAMODE)—RO. Hardwired to 0. This means that when acting as a master
on AGP and a Master Abort occurs, the MCH will discard data on writes and return all 1s during
reads.
4
Reserved.
3
VGA Enable (VGA_EN1)—R/W. This bit controls the routing of host-initiated transactions
targeting VGA compatible I/O and memory address ranges.
0 =VGA compatible memory and I/O range accesses are not forwarded to AGP (Default). Rather,
they are mapped to primary PCI unless they are mapped to AGP via I/O and memory range
registers defined above (IOBASE1, IOLIMIT1, MBASE1, MLIMIT1, PMBASE1, PMLIMIT1)
1 =MCH forwards the following host accesses to the AGP:
• Memory accesses in the range 0A0000h to 0BFFFFh
• I/O addresses where A[9:0] are in the ranges 3B0h to 3BBh and 3C0h to 3DFh
(inclusive of ISA address aliases - A[15:10] are not decoded)
When this bit is set, forwarding of these accesses issued by the host is independent of the I/O
address and memory address ranges defined by the previously defined base and limit
registers. Forwarding of these accesses is also independent of the settings of bit 2 (ISA
Enable) of this register if this bit is 1.
Refer to Chapter 4 for further information.
2
ISA Enable (ISA_EN)—R/W. Modifies the response by the MCH to an I/O access issued by the
host that targets ISA I/O addresses. This applies only to I/O addresses that are enabled by the
IOBASE and IOLIMIT registers.
0 =Disable. All addresses defined by the IOBASE and IOLIMIT Registers for host I/O
transactions are mapped to AGP (Default).
1 =Enable. MCH does not forward to AGP any I/O transactions addressing the last 768 bytes in
each 1 KB block, even if the addresses are within the range defined by the IOBASE and
IOLIMIT registers. Instead of going to AGP, these cycles are forwarded to PCI0 where they
can be subtractively or positively claimed by the ISA bridge.
1
92
Reserved.
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Intel 82845 MCH for SDR Datasheet
Register Description
R
Bit
Descriptions
0
Parity Error Response Enable (PER_EN)—R/W. Controls MCH’s response to data phase parity
errors on AGP.
0 =Address and data parity errors on AGP are not reported via the MCH hub interface SERR#
messaging mechanism. Other types of error conditions can still be signaled via SERR#
messaging independent of this bit’s state.
1 =The G_PERR# signal is not implemented by the MCH. However, when this bit is set to 1,
address and data parity errors detected on AGP are reported via hub interface SERR#
messaging mechanism, if further enabled by SERRE1.
3.6.22
ERRCMD1—Error Command Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
Bit
7:1
0
40h
00h
R/W
8 bits
Description
Reserved.
SERR on Receiving Target Abort (SERTA).
0 = MCH does not assert an SERR message upon receipt of a target abort on AGP. SERR
messaging for Device 1 is globally enabled in the PCICMD1 register.
1 = MCH generates an SERR message over the hub interface when a target abort is received on
AGP.
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Register Description
R
3.6.23
DWTC—DRAM Write Thermal Management Control
Register (Device 1)
Address Offset:
Default Value:
Access:
Size:
Bit
50–57h
00h
R/W/L
64 bits
Descriptions
63:41
Reserved.
40:28
Global Write Hexword Threshold (GWHT). The 13-bit value in this field is multiplied by 215 to
arrive at the number of hexwords that must be written within the Global DRAM Write Sampling
Window to cause the thermal management mechanism to be invoked.
27:22
Write Thermal Management Time (WTMT). This value provides a multiplier between 0 and 63
that specifies how long thermal management remains in effect as a number of Global DRAM
Write Sampling Windows. For example, if GDWSW is programmed to
1000_0000b and WTT is set to 01_0000b, then thermal management will be performed for
8192*105 host clocks (@ 100 MHz) seconds once invoked (128 * 4*105 host clocks * 16).
21:15
Write Thermal Management Monitoring Window (WTMMW). The value in this register is
padded with four 0s to specify a window of 0–2047 host clocks with a 16-clock granularity.
While the thermal management mechanism is invoked, system memory writes are monitored
during this window. If the number of hexwords written during the window reaches the Write
Thermal Management Hexword Maximum (bits 14:3), then write requests are blocked for the
remainder of the window.
14:3
Write Thermal Management Hexword Maximum (WTMHM). The Write Thermal
Management Hexword Maximum defines the maximum number of hexwords between 0–4095
that are permitted to be written to system memory within one Write Thermal Management
Monitoring Window.
2:1
Write Thermal Management Mode (WTMMode).
00 = Thermal management via Counters and Hardware Thermal Management_on signal
mechanisms disabled.
01 = Hardware Thermal Management_on signal mechanism is enabled. In this mode, as long
as the Thermal Management_on signal is asserted, write thermal management is in effect
based on the settings in WTMW and WTHM. When the Thermal Management_on signal is
deasserted, write thermal management stops and the counters associated with the
WTMW and WTHM are reset. When the hardware Thermal Management_on signal
mechanism is not enabled, the Thermal Management_on signal has no effects.
10 = Counter mechanism controlled through GDWSW and GWHT is enabled. When the
threshold set in GDWSW and GWHT is reached, thermal management start/stop cycles
occur based on the settings in WTT, WTMW and WTHM.
11 = Reserved.
0
START Write Thermal Management (SWTM). Software writes to this bit to start and stop write
thermal management.
0 = Write thermal management stops and the counters associated with WTMW and WTHM are
reset.
1 = Write thermal management begins based on the settings in WTMW and WTHM, and
remains in effect until this bit is reset to 0.
0
94
Reserved.
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Intel 82845 MCH for SDR Datasheet
Register Description
R
3.6.24
DRTC—DRAM Read Thermal Management Control Register
(Device 1)
Address Offset:
Default Value:
Access:
Size:
Bit
58–5Fh
0000_0000_0000_0000h
R/W/L
64 bits
Descriptions
63:41
Reserved.
40:28
Global Read Hexword Threshold (GRHT). The thirteen-bit value held in this field is multiplied by
215 to arrive at the number of hexwords that must be written within the Global DRAM Read
Sampling Window to cause the thermal management mechanism to be invoked.
27:22
Read Thermal Management Time (RTMT). This value provides a multiplier between 0 and 63
that specifies how long counter-based read thermal management remains in effect as a number
of Global DRAM Read Sampling Windows. For example, if GDRSW is programmed to
1000_0000b and RTT is set to 01_0000b, then read thermal management will be performed for
8192*105 host clocks (@ 100 MHz) seconds once invoked (128 * 4*105 host clocks * 16).
21:15
Read Thermal Management Monitoring Window (RTMMW). The value in this register is
padded with four 0s to specify a window of 0–2047 host clocks with 16-clock granularity. While
the thermal management mechanism is invoked, system memory reads are monitored during this
window. If the number of hexwords read during the window reaches the Read Thermal
Management Hexword Maximum (bits 14:3), then read requests are blocked for the remainder of
the window.
14:3
Read Thermal Management Hexword Maximum (RTMHM). This field defines the maximum
number of hexwords between 0–4095 that are permitted to be read from system memory within
one Read Thermal Management Monitoring Window.
2:1
Read Thermal Management Mode (RTMMode).
00 = Thermal management via counters and Hardware Thermal Management_on signal
mechanisms disabled.
01 = Hardware Thermal Management_on signal mechanism is enabled. In this mode, as long as
the Thermal Management_on signal is asserted, read thermal management is in effect
based on the settings in RTMW and RTHM. When the Thermal Management_on signal is
deasserted, read thermal management stops and the counters associated with the RTMW
and RTHM are reset. When the hardware Thermal Management_on signal mechanism is
not enabled, the Thermal Management_on signal has no effects.
10 = Counter mechanism controlled through GDRSW and GRHT is enabled. When the threshold
set in GDRSW and GRHT is reached, thermal management start/stop cycles occur based
on the settings in RTT, RTMW and RTHM.
11 = Reserved.
0
START Read Thermal Management (SRTM). Software writes to this bit to start and stop read
thermal management.
0 = Read thermal management stops and the counters associated with RTMW and RTHM are
reset.
1 = Read thermal management begins based on the settings in RTMW and RTHM, and remains
to be in effect until this bit is reset to 0.
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Register Description
R
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System Address Map
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4
System Address Map
A system based on the 845 chipset supports 4 GB of addressable memory space and 64 KB+3 of
addressable I/O space. The I/O and memory spaces are divided by system configuration software
into regions. The memory ranges are useful either as system memory or as specialized memory,
while the I/O regions are used solely to control the operation of devices in the system.
When the MCH receives a write request whose address targets an invalid space, the data is
ignored. For reads, the MCH responds by returning all zeros on the requesting interface.
4.1
Memory Address Ranges
The system memory map is broken into two categories:
• Extended Memory Range (1 MB to 4 GB). The second is extended memory, existing
between 1MB and 4GB. It contains a 32-bit memory space, which is used for mapping PCI,
AGP, APIC, SMRAM, and BIOS memory spaces.
• DOS Compatible Area (below 1 MB). The final range is a DOS legacy space, which is used
for BIOS and legacy devices on the LPC interface.
Figure 3. Addressable Memory Space
16 GB
Additional System
M em ory Address
Range
4 GB
PCI Mem ory Address
Range
Hub Interface
AG P
Graphics
Aperture
I/O
Aperture
APICs
Top of Low
Mem ory
System M em ory
Address Range
1 MB
DOS Legacy Address
Range
Independently Program m able
Non-overlapping W indows
sys_addr_map_1
These address ranges are always mapped to system memory, regardless of the system
configuration. Memory may be taken out of the system memory segment for use by System
Management Mode (SMM) hardware and software. The Top of Low Memory (TOM) register
defines the top of system memory.
Note that the address of the highest 16 MB quantity of valid memory in the system is placed into
the GBA15 register. For memory populations <3 GB, this value will be the same as the one
programmed into the TOM register. For other memory configurations, the two are unlikely to be
the same, since the PCI configuration portion of the BIOS software will program the TOM register
to the maximum value that is less than the amount of memory in the system and that allows enough
room for all populated PCI devices.
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System Address Map
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Figure 4. DOS Compatible Area Address Map
1 MB
Upper, Lower,
Expansion Card BIOS
and Buffer Area
Controlled by
PAM[6:0]
0C0000h
0B8000h
Standard PCI/ISA
Video Mem ory
(SMM Mem ory)
768 KB
736 KB
Monochrom e Display
Adapter Space
0B0000h
704 KB
0A0000h
640 KB
Controlled by
VGA Enable and
MDA Enable
= Optional AGP
= Optional System Mem ory
= System Mem ory
sys_addr_map_2
Figure 5. Extended Memory Range Address Map
1_0000_0000 (4 G B)
High BIO S, Optional
extended SM RAM
FF00_0000
Hub Interface
(always)
FEF0_0000
Local APIC Space
FEE0_0000
Hub Interface
(always)
FED0_0000
I/O APIC Space
FEC8_0000
I/O APIC Space
FEC0_0000
AGP/PCI
T op of Low Mem ory (TOM)
Extended SMRAM
Space
T EM - TSEG
100C_0000
Extended SMRAM
(translated to < 1 M B)
100A_0000
0100_0000 (16 MB)
ISA Hole
=
System Mem ory Region
=
Optional System Mem ory Region
00F0_0000 (15 MB)
0010_0000 (1 MB)
sys_addr_map_3
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System Address Map
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4.1.1
VGA and MDA Memory Space
Video cards use these legacy address ranges to map a frame buffer or a character-based video
buffer. The address ranges in this memory space are:
• VGAA
0_000A_0000 to 0_000A_FFFF
• MDA
0_000B_0000 to 0_000B_7FFF
• VGAB
0_000B_8000 to 0_000B_FFFF
By default, accesses to these ranges are forwarded to the hub interface. However, if the VGA_EN1
bit is set in the BCTRL1 configuration register, transactions within the VGA and MDA spaces are
sent to AGP. If the MCHCFG.MDAP configuration bit is set, accesses that fall within the MDA
range are sent to the hub interface independent of the setting of the VGA_EN1 bit.
If the MCHCFG.MDAP configuration bit is set, accesses in the MDA range are sent to the hub
interface, independent of the setting of the VGA_EN1 bit. Legacy support requires the ability to
have a second graphics controller (monochrome) in the system. In an 845 chipset system, accesses
in the standard VGA range are forwarded to AGP. Since the monochrome adapter may be on the
hub interface or (or ISA) bus, the MCH must decode cycles in the MDA range and forward them
to the hub interface. This capability is controlled by a configuration bit (MCHCFG.MDAP). In
addition to the memory range B0000h to B7FFFh, the MCH decodes I/O cycles at 3B4h, 3B5h,
3B8h, 3B9h, 3BAh, and 3BFh and forwards them to the hub interface.
An optimization allows the system to reclaim the memory displaced by these regions. If SMM
memory space is enabled by SMRAM.G_SMRARE and either the SMRAM.D_OPEN bit is set or
the system bus receives an SMM-encoded request for code (not data), then the transaction is
steered to system memory rather than the hub interface. Under these conditions, the VGA_EN1 bit
and the MDAP bit are ignored.
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System Address Map
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4.1.2
PAM Memory Spaces
The address ranges in this memory space are:
• PAMC0
0_000C_0000 to 0_000C_3FFF
• PAMC4
0_000C_4000 to 0_000C_7FFF
• PAMC8
0_000C_8000 to _000C_BFFF
• PAMCC
0_000C_C000 to 0_000C_FFFF
• PAMD0
0_000D_0000 to 0_000D_3FFF
• PAMD4
0_000D_4000 to 0_000D_7FFF
• PAMD8
0_000D_8000 to 0_000D_BFFF
• PAMDC
0_000D_C000 to 0_000D_FFFF
• PAME0
0_000E_0000 to 0_000E_3FFF
• PAME4
0_000E_4000 to 0_000E_7FFF
• PAME8
0_000E_8000 to 0_000E_BFFF
• PAMEC
0_000E_C000 to 0_000E_FFFF
• PAMF0
0_000F_0000 to 0_000F_FFFF
The 256 KB PAM region is divided into three parts:
• ISA expansion region; 128 KB area between 0_000C_0000h–0_000D_FFFFh
• Extended BIOS region; 64 KB area between 0_000E_0000h–0_000E_FFFFh
• System BIOS region; 64 KB area between 0_000F_0000h–0_000F_FFFFh.
The ISA expansion region is divided into eight 16 KB segments. Each segment can be assigned
one of four read/write states: read-only, write-only, read/write, or disabled. Typically, these blocks
are mapped through MCH and are subtractively decoded to ISA space.
The extended system BIOS region is divided into four 16 KB segments. Each segment can be
assigned independent read and write attributes so it can be mapped either to main system memory
or to the hub interface. Typically, this area is used for RAM or ROM.
The system BIOS region is a single 64 KB segment. This segment can be assigned read and write
attributes. It is by default (after reset) read/write disabled and cycles are forwarded to the hub
interface. By manipulating the read/write attributes, the MCH can “shadow” BIOS into system
memory.
4.1.3
ISA Hole Memory Space
BIOS software may optionally open a “window” between 15 MB and 16 MB (0_00F0_0000h to
0_00FF_FFFFh) that relays transactions to the hub interface instead of completing them with a
system memory access. This window is opened by programming the FDHC.HEN configuration
field.
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4.1.4
TSEG SMM Memory Space
The TSEG SMM space (TOM – TSEG to TOM) allows system management software to partition
a region of system memory just below the top of low memory (TOM) that is accessible only by
system management software. This region may be 128 KB, 256 KB, 512 KB, or 1 MB in size,
depending on the ESMRAMC.TSEG_SZ field. SMM memory is globally enabled by
SMRAM.G_SMRAME. Requests can access SMM system memory when either SMM space is
open (SMRAM.D_OPEN) or the MCH receives an SMM code request on its system bus. To
access the TSEG SMM space, TSEG must be enabled by ESMRAMC.T_EN. When all of these
conditions are met, then a system bus access to the TSEG space (between TOM–TSEG and TOM)
is sent to system memory. If the high SMRAM is not enabled or if the TSEG is not enabled, then
all memory requests from all interfaces are forwarded to system memory. If the TSEG SMM space
is enabled, and an agent attempts a non-SMM access to TSEG space, then the transaction is
specially terminated.
Note: Hub interface and AGP originated accesses are not allowed to SMM space.
4.1.5
IOAPIC Memory Space
The IOAPIC space (0_FEC0_0000h to 0_FEC7_FFFFh) is used to communicate with IOAPIC
interrupt controllers that may be populated on the hub interface. Since it is difficult to relocate an
interrupt controller using plug-and-play software, fixed address decode regions have been
allocated for them. Processor accesses to the IOAPIC0 region are always sent to the hub interface.
4.1.6
System Bus Interrupt APIC Memory Space
The system bus interrupt space (0_FEE0_0000h to 0_FEEF_FFFFh) is the address used to deliver
interrupts to the system bus. Any device on AGP may issue a memory write to 0FEEx_xxxxh. The
MCH forwards this memory write, along with the data, to the system bus as an Interrupt Message
Transaction. The MCH terminates the system bus transaction by providing the response and
asserting TRDY#. This memory write cycle does not go to system memory.
4.1.7
High SMM Memory Space
The HIGHSMM space (0_FEDA_0000h to 0_FEDB_FFFFh) allows cacheable access to the
compatible SMM space by re-mapping valid SMM accesses between 0_FEDA_0000 and
0_FEDB_FFFF to accesses between 0_000A_0000 and 0_000B_FFFF. The accesses are
remapped when SMRAM space is enabled; an appropriate access is detected on the system bus,
and when ESMRAMC.H_SMRAME allows access to high SMRAM space. SMM memory
accesses from any hub interface or AGP are specially terminated: reads are provided with the
value from address 0 while writes are ignored entirely.
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4.1.8
AGP Aperture Space (Device 0 BAR)
Processors and AGP devices communicate through a special buffer called the “graphics aperture”
(APBASE to APBASE + APSIZE). This aperture acts as a window into main system memory and
is defined by the APBASE and APSIZE configuration registers of the MCH. Note that the AGP
aperture must be above the top of memory and must not intersect with any other address space.
4.1.9
AGP Memory and Prefetchable Memory
Plug-and-play software configures the AGP memory window to provide enough memory space for
the devices behind this PCI-to-PCI bridge. Accesses whose addresses fall within this window are
decoded and forwarded to AGP for completion. The address ranges are:
• M1
MBASE1 to MLIMIT1
• PM1
PMBASE1 to PMLIMIT1
Note that these registers must be programmed with values that place the AGP memory space
window between the value in the TOM register and 4 GB. In addition, neither region should
overlap with any other fixed or relocatable area of memory.
4.1.10
Hub Interface Subtractive Decode
All accesses that fall between the value programmed into the TOM register and 4 GB
(i.e., TOM to 4 GB) are subtractively decoded and forwarded to the hub interface if they do not
decode to a space that corresponds to another device.
4.2
AGP Memory Address Ranges
The MCH can be programmed to direct memory accesses to the AGP bus interface when
addresses are within either of two ranges specified via registers in MCH device 1 configuration
space. The first range is controlled via the Memory Base Address (MBASE1) register and
Memory Limit Address (MLIMIT1) register. The second range is controlled via the Prefetchable
Memory Base Address (PMBASE1) register and Prefetchable Memory Limit Address
(PMLIMIT1) register
The MCH positively decodes memory accesses to AGP memory address space as defined by the
following equations:
• Memory_Base_Address ≤ Address ≤ Memory_Limit_Address
• Prefetchable_Memory_Base_Address ≤ Address ≤ Prefetchable_Memory_Limit_Address
The plug-and-play configuration software programs the effective size of the range and it depends
on the size of memory claimed by the AGP device.
Note: The MCH device 1 memory range registers described above are used to allocate memory address
space for any devices sitting on AGP bus that require such a window.
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4.2.1
AGP DRAM Graphics Aperture
Memory-mapped, graphics data structures can reside in a Graphics Aperture to system memory.
This aperture is an address range defined by the APBASE and APSIZE registers of the MCH
device 0. The APBASE register follows the standard base address register template as defined by
the PCI Local Bus Specification, Revision 2.1. The size of the range claimed by the APBASE is
programmed via “back-end” register APSIZE (programmed by the chipset specific BIOS before
plug-and-play session is performed). APSIZE allows the BIOS software to pre-configure the
aperture size to be 4 MB, 8 MB, 16 MB, 32 MB, 64 MB, 128 MB or 256 MB. By programming
APSIZE to a specific size, the corresponding lower bits of APBASE are forced to 0 (behave as
hardwired). The default value of APSIZE forces an aperture size of 256 MB. The aperture address
range is naturally aligned.
Accesses within the aperture range are forwarded to the system memory subsystem. The MCH
translates the originally issued addresses via a translation table maintained in system memory. The
aperture range should be programmed as non-cacheable in the processor caches.
Note: Plug-and-play software configuration model does not allow overlap of different address ranges.
Therefore the AGP Graphics Aperture and AGP memory address range are independent address
ranges that may abut, but cannot overlap one another.
4.3
System Management Mode (SMM) Memory Range
The MCH supports the use of system memory as System Management RAM (SMRAM) enabling
the use of System Management Mode. The MCH supports three SMRAM options: Compatible
SMRAM (C_SMRAM), High Segment (HSEG), and Top of Memory Segment (TSEG). System
Management RAM (SMRAM) space provides a memory area that is available for the SMI
handler’s and code and data storage. This memory resource is normally hidden from the system
OS so that the processor has immediate access to this memory space upon entry to SMM. The
MCH provides three SMRAM options:
• Below 1 MB option that supports compatible SMI handlers.
• Above 1 MB option that allows new SMI handlers to execute with write-back cacheable
SMRAM.
• Optional larger write-back cacheable T_SEG area from 128 KB to 1 MB in size above 1 MB
that is reserved from the highest area in system memory. The above 1 MB solutions require
changes to compatible SMRAM handlers’ code to properly execute above 1 MB.
Note: Masters from the hub interface and AGP are not allowed to access the SMM space.
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4.3.1
SMM Space Definition
Its addressed SMM space and its DRAM SMM space define SMM space. The addressed SMM
space is defined as the range of bus addresses used by the processor to access SMM space. System
memory SMM space is defined as the range of physical system memory locations containing the
SMM code. SMM space can be accessed at one of three transaction address ranges: Compatible,
High, and TSEG. The Compatible and TSEG SMM space is not remapped and, therefore, the
addressed and DRAM SMM space is the same address range. Since the High SMM space is
remapped the addressed and system memory SMM space is a different address range. Note that the
High system memory space is the same as the Compatible Transaction Address space. Therefore,
the table below describes three unique address ranges:
• Compatible Transaction Address
• High Transaction Address
• TSEG Transaction Address
Table 11. SMM Space Address Ranges
SMM Space Enabled
Compatible
Transaction Address Space
System Memory Space
A0000h to BFFFFh
A0000h to BFFFFh
High
0FEDA0000h to 0FEDBFFFFh
A0000h to BFFFFh
TSEG
(TOM–TSEG_SZ) to TOM
(TOM–TSEG_SZ) to TOM
Note: High SMM: This is different than in some previous chipsets where the High segment was the
384 KB region from A0000h to FFFFFh.
Note: TSEG SMM: Note that this is different than in previous chipsets where the TSEG address space
was offset by 256 MB to allow for simpler decoding and the TSEG was remapped to just under the
TOM. In the MCH the 256 MB does not offset the TSEG region and it is not remapped.
4.3.2
SMM Space Restrictions
If any of the following conditions are violated, the results of SMM accesses are unpredictable and
may cause the system to hang:
• The Compatible SMM space must not be setup as cacheable.
• High or TSEG SMM transaction address space must not overlap address space assigned to
system memory, the AGP aperture range, or to any “PCI” devices (including hub interface and
AGP devices). This is a BIOS responsibility.
• Both D_OPEN and D_CLOSE must not be set to 1 at the same time.
• When TSEG SMM space is enabled, the TSEG space must not be reported to the OS as
available system memory. This is a BIOS responsibility.
• Any address translated through the AGP Aperture GTLB must not target system memory from
000A0000h to 000FFFFFh.
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4.4
I/O Address Space
The MCH does not support the existence of any other I/O devices beside itself on the system bus.
The MCH generates either hub interface or AGP bus cycles for all processor I/O accesses. The
MCH contains two internal registers in the processor I/O space: Configuration Address
(CONF_ADDR) register and Configuration Data (CONF_DATA) register. These locations are
used to implement the PCI configuration space access mechanism and as described in Chapter 3.
The processor allows 64 KB+3 bytes to be addressed within the I/O space. The MCH propagates
the processor I/O address without any translation on to the destination bus and therefore provides
addressability for 64 KB+3 byte locations. Note that the upper 3 locations can be accessed only
during I/O address wrap-around when signal A16# address signal is asserted. A16# is asserted on
the system bus whenever an I/O access is made to 4 bytes from address 0FFFDh, 0FFFEh, or
0FFFFh. A16# is also asserted when an I/O access is made to 2 bytes from address 0FFFFh.
The I/O accesses (other than ones used for configuration space access) are forwarded normally to
the hub interface unless they fall within the AGP I/O address range as defined by the mechanisms
explained below. The MCH does not post I/O write cycles to IDE.
The MCH never responds to I/O or configuration cycles initiated on AGP or the hub interface.
Hub interface transactions requiring completion are terminated with “master abort” completion
packets on the hub interface. Hub interface write transactions not requiring completion are
dropped. AGP/PCI I/O reads are never acknowledged by the MCH.
4.5
Intel® MCH Decode Rules and Cross-Bridge
Address Mapping
The address map described above applies globally to accesses arriving on any of the three
interfaces (i.e., processor system bus, hub interface, or AGP).
4.5.1
Hub Interface Decode Rules
The MCH accepts accesses from the hub interface with the following address ranges:
• All memory read and write accesses to main DRAM (except SMM space).
• All memory write accesses from the hub interface to AGP memory range defined by
MBASE1, MLIMIT1, PMBASE1, and PMLIMIT1.
• All memory read/write accesses to the Graphics Aperture defined by APBASE and APSIZE.
• Memory writes to VGA range on AGP if enabled.
All memory reads from the hub interface that target >4 GB memory range are terminated with a
master abort completion, and all memory writes (>4 GB) from the hub interface are ignored.
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4.5.2
AGP Interface Decode Rules
Cycles Initiated Using AGP FRAME# Protocol
The MCH does not support any AGP FRAME# access targeting the hub interface. The MCH
claims AGP-initiated memory read and write transactions decoded to the system memory range or
the Graphics Aperture range. All other memory read and write requests will be master-aborted by
the AGP initiator as a consequence of MCH not responding to a transaction.
Under certain conditions, the MCH restricts access to the DOS Compatibility ranges governed by
the PAM registers by distinguishing access type and destination bus. The MCH does NOT accept
AGP FRAME# write transactions to the compatibility ranges if the PAM designates system
memory as writeable. If accesses to a range are not write-enabled by the PAM, the MCH does not
respond and the cycle results in a master-abort. The MCH accepts AGP FRAME# read
transactions to the compatibility ranges if the PAM designates system memory as readable. If
accesses to a range are not read-enabled by the PAM, the MCH does not respond and the cycle
results in a master-abort.
If agent on AGP issues an I/O, PCI Configuration or PCI Special Cycle transaction, the MCH does
not respond and cycle results in a master-abort.
Cycles Initiated Using AGP PIPE# or SB Protocol
All cycles must reference system memory; that is, system memory address range (including PAM)
or Graphics Aperture range (also physically mapped within system memory but using different
address range). AGP accesses to SMM space are not allowed. AGP-initiated cycles that target
system memory are not snooped on the host bus, even if they fall outside of the AGP aperture
range.
If a cycle is outside of the system memory range, then it terminates as follows:
• Reads remap to memory address 0h, return data from address 0h, and set the IAAF error bit in
ERRSTS register in device 0
• Writes are terminated internally without affecting any chip signals or system memory
AGP Accesses to MCH that Cross Device Boundaries
For AGP FRAME# accesses, when an AGP master gets disconnected, it resumes at the new
address which allows the cycle to be routed to or claimed by the new target. Therefore, the target
on potential device boundaries should disconnect accesses. The MCH disconnects AGP FRAME#
transactions on 4 KB boundaries.
AGP PIPE# and SBA accesses are limited to 256 bytes and must hit system memory. Read
accesses crossing a device boundary will return invalid data when the access crosses out of system
memory. Write accesses crossing out of system memory will be discarded. The IAAF Error bit will
be set.
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5
Functional Description
This chapter describes the system bus that connects the MCH to the processor, the system memory
interface, the AGP interface, the MCH power and thermal management, the MCH clocking, and
the MCH system reset and power sequencing.
5.1
System Bus
The MCH supports the Pentium 4 processor subset of the Enhanced Mode Scaleable Bus. Source
synchronous transfers are used for the address and data signals. The address signals are double
pumped and a new address can be generated every other bus clock. At 100 MHz bus frequency,
the address signals run at 200 MT/s for a maximum address queue rate of 50 M addresses/sec. The
data is quad pumped and an entire 64-byte cache line can be transferred in two bus clocks. At
100 MHz bus frequency, the data signals run at 400 MT/s for a maximum bandwidth of 3.2 GB/s.
The MCH supports a 12 deep IOQ.
The MCH supports two outstanding deferred transactions on the system bus. The two transactions
must target different I/O interfaces as only one deferred transaction can be outstanding to any
single I/O interface at a time.
5.1.1
Dynamic Bus Inversion
The MCH supports Dynamic Bus Inversion (DBI) when driving and receiving data from the
system bus. DBI limits the number of data signals that are driven to a low voltage on each quad
pumped data phase. This decreases the power consumption of the MCH. DBI[3:0]# indicates if the
corresponding 16 bits of data are inverted on the bus for each quad pumped data phase:
DBI[3:0]#
Data Bits
DBI0#
HD[15:0]#
DBI1#
HD[31:16]#
DBI2#
HD[47:32]#
DBI3#
HD[63:48]#
When the processor or the MCH drives data, each 16-bit segment is analyzed. If more than 8 of
the 16 signals would normally be driven low on the bus, the corresponding DBI# signal will be
asserted and the data will be inverted prior to being driven on the bus. When the processor or the
MCH receives data, it monitors DBI[3:0]# to determine if the corresponding data segment should
be inverted.
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5.1.2
System Bus Interrupt Delivery
The Pentium 4 processor supports the system bus interrupt delivery; the APIC serial bus interrupt
delivery mechanism is not supported. Interrupt-related messages are encoded on the system bus as
“Interrupt Message Transactions”. In an 845 chipset platform, system bus interrupts can originate
from the processor on the system bus, or from a downstream device on the hub interface or AGP.
In the later case the MCH drives the “Interrupt Message Transaction” onto the system bus.
In an 845 chipset platform, the ICH2 contains IOxAPICs, and its interrupts are generated as
upstream hub interface memory writes. Furthermore, PCI 2.2 defines MSIs (Message Signaled
Interrupts) that are also in the form of memory writes. A PCI 2.2 device can generate an interrupt
as an MSI cycle on it’s PCI bus, instead of asserting a hardware signal to the IOxAPIC. The MSI
can be directed to the IOxAPIC, which in turn generates an interrupt as an upstream hub interface
memory write. Alternatively, the MSI can be directed directly to the system bus. The target of a
MSI is dependent on the address of the interrupt memory write. The MCH forwards inbound hub
interface and AGP (PCI semantic only) memory writes to address 0FEEx_xxxxh, to the system bus
as “Interrupt Message Transactions”.
5.1.3
Upstream Interrupt Messages
The MCH accepts message-based interrupts from AGP (PCI semantics only) or its hub interface
and forwards them to the system bus as Interrupt Message Transactions. The interrupt messages
presented to the MCH are in the form of memory writes to address 0FEEx_xxxxh. At the hub
interface or AGP interface, the memory write interrupt message is treated like any other memory
write; it is either posted to the inbound data buffer (if space is available) or retried (if data buffer
space is not immediately available). Once posted, the memory write from AGP or the hub interface
to address 0FEEx_xxxxh is decoded as a cycle that needs to be propagated by the MCH to the
system bus as an Interrupt Message Transaction.
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5.2
System Memory Interface
The 845 chipset can be configured to support PC133 SDRAM.
5.2.1
Single Data Rate (SDR) SDRAM Interface Overview
The MCH integrates a system memory SDRAM controller with a 64-bit wide interface and twelve
system memory clock signals (each at 133 MHz). The MCH’s system memory buffers support
LVTTL (SDRAM) signaling at 133 MHz.
The MCH includes support for:
• Up to 3 GB of 133 MHz SDR SDRAM
• PC133 unbuffered 168 pin SDR SDRAM DIMMs
• Maximum of 3 DIMMs, single-sided and/or double-sided
• Configurable optional ECC
The two bank-select lines SBS[1:0] and the thirteen address lines (SMA[12:0]) allow the MCH to
support 64-bit wide DIMMs using 64 Mb, 128 Mb, 256 Mb, and 512 Mb SDRAM technologies.
While address lines SMA[9:0] determine the starting address for a burst, burst lengths are fixed at
four. Twelve chip selects SCS# lines allow a maximum of three rows of single-sided SDRAM
DIMMs and six rows of double-sided SDRAM DIMMs.
The MCH’s system memory controller targets CAS latencies of 2 and 3 clocks for SDRAM. The
MCH provides refresh functionality with a programmable rate (normal SDRAM rate is
1 refresh/15.6 us).
5.2.2
Memory Organization and Configuration
In the following discussion the term row refers to a set of memory devices that are simultaneously
selected by a SCS# signal. The MCH supports a maximum of 6 rows of memory. For the purposes
of this discussion, a “side” of a DIMM is equivalent to a “row” of SDRAM devices.
Table 12. Supported DIMM Configurations
Density
®
64 Mbit
128 Mbit
256 Mbit
512 Mbit
Device
Width
X8
X16
X8
X16
X8
X16
X8
X16
Single \
Double
SS/DS
SS/DS
SS/DS
SS/DS
SS/DS
SS/DS
SS/DS
SS/DS
168 pin
SDR
DIMMs
64 MB /
128 MB
32 MB /
64 MB
128 MB /
256 MB
64 MB /
128 MB
256 MB /
512 MB
128 MB /
256 MB
512 MB /
1024 MB
256 MB /
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5.2.2.1
Configuration Mechanism For DIMMs
Detection of the type of SDRAM installed on the DIMM is supported via a Serial Presence Detect
mechanism as defined in the JEDEC 168-pin DIMM specification. This uses the SCL, SDA and
SA[2:0] pins on the DIMMs to detect the type and size of the installed DIMMs. No special
programmable modes are provided on the MCH for detecting the size and type of memory
installed. Type and size detection must be done via the serial presence detection pins.
Memory Detection and Initialization
Before any cycles to the memory interface can be supported, the MCH SDRAM registers must be
initialized. The MCH must be configured for operation with the installed memory types. Detection
of memory type and size is accomplished via the System Management Bus (SMBus) interface on
the ICH2. This two-wire bus is used to extract the SDRAM type and size information from the
Serial Presence Detect port on the SDRAM DIMMs. SDRAM DIMMs contain a 5-pin Serial
Presence Detect interface, including SCL (serial clock), SDA (serial data), and SA[2:0]. Devices
on the SMBus bus have a seven-bit address. For the SDRAM DIMMs, the upper four bits are
fixed at 1010. The lower three bits are strapped on the SA[2:0] pins. SCL and SDA are connected
directly to the system management bus on the ICH2. Thus, data is read from the Serial Presence
Detect port on the DIMMs via a series of I/O cycles to the ICH2. BIOS needs to determine the
size and type of memory used for each of the rows of memory to properly configure the MCH
memory interface.
SMBus Configuration and Access of the Serial Presence Detect Ports
For more details on SMBus Configuration and Serial Present Detect Ports, see the Intel® 82801BA
I/O Controller Hub 2 (ICH2) and 82801BAM I/O Controller Hub 2 Mobile (ICH2-M) Datasheet.
Memory Register Programming
This section provides an overview of how the required information for programming the SDRAM
registers is obtained from the Serial Presence Detect ports on the DIMMs. The Serial Presence
Detect ports are used to determine refresh rate, MA and MD buffer strength, row type (on a row by
row basis), SDRAM Timings, row sizes and row page sizes. Table 13 lists a subset of the data
available through the on-board Serial Presence Detect ROM on each DIMM.
Table 13. Data Bytes on DIMM Used for Programming DRAM Registers
Byte
Function
2
Memory type (SDR SDRAM or DDR SDRAM)
3
Number of row addresses, not counting bank addresses
4
Number of column addresses
5
Number of banks of SDRAM (single- or double-sided DIMM)
11
ECC, no ECC
12
Refresh rate
17
Number banks on each device
Table 13 is only a subset of the defined SPD bytes on the DIMMs. These bytes collectively
provide enough data for programming the MCH SDRAM registers.
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5.2.3
Memory Address Translation and Decoding
The 845 MCH contains address decoders that translate the address received on the system bus or
the hub interface. Decoding and translation of these addresses vary with the four SDRAM types.
Also, the number of pages, page sizes, and densities supported vary with the type. In general, the
MCH supports 64 Mb, 128 Mb, 256 Mb, and 512 Mb SDRAM devices. The multiplexed
row/column address to the SDRAM memory array is provided by the SBS[1:0] and SMA[12:0]
signals. These addresses are derived from the system address bus as defined by Table 14 for
SDRAM devices.
Table 14. Address Translation and Decoding
Tech.
Configuration
64 Mb
1Meg x 16 x 4 bks
Row size
Row / Row Addr
Page size Column / Col
Bank
32 MB
12x8x2
2 KB
64 Mb
2Meg x 8 x 4 bks
64 MB
64 MB
12x9x2
128 MB
12x9x2
128 MB
12x10x2
256 MB
13x9x2
256 MB
13x10x2
512 MB
13x10x2
13
12
24
Row
Row
Row
Row
Row
13x11x2
Intel 82845 MCH for SDR Datasheet
Row
Col
14
25
14
AP
25
13
12
24
25
14
AP
26
14
13
26
26
13
12
26
24
15
16
23
22
21
20
19
18
17
10
9
8
7
6
5
4
3
15
16
23
22
21
20
19
18
17
11
10
9
8
7
6
5
4
3
15
16
23
22
21
20
19
18
17
11
10
9
8
7
6
5
4
3
25
24
15
16
23
22
21
20
19
18
17
AP
12
11
10
9
8
7
6
5
4
3
25
14
15
16
23
22
21
20
19
18
17
11
10
9
8
7
6
5
4
3
AP
27
14
13
27
26
25
24
15
16
23
22
21
20
19
18
17
AP
12
11
10
9
8
7
6
5
4
3
27
14
13
27
25
24
15
16
23
22
21
20
19
18
17
AP
12
11
10
9
8
7
6
5
4
3
26
25
24
28
16
23
22
21
20
19
18
17
13
AP
12
11
10
9
8
7
6
5
4
3
26
Col
16 KB
®
25
Col
8 KB
512 Mb 16Meg x 8 x 4bks
Row
13
AP
Col
8 KB
512 Mb 8Meg x 16 x 4bks
24
Col
4 KB
256 Mb 8Meg x 8 x 4 bks
12
Col
8 KB
256 Mb 4Meg x 16 x 4 bks
11
Col
4 KB
128 Mb 4Meg x 8 x 4bks
24
Col
4 KB
128 Mb 2Meg x 16 x 4bks
Row
BA1 BA0 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
28
14
15
27
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5.2.4
DRAM Performance Description
The overall memory performance is controlled by the DRAM Timing (DRT) Register, pipelining
depth used in the MCH, memory speed grade, and the type of SDRAM used in the system. In
addition, the exact performance in a system is also dependent on the total memory supported,
external buffering, and memory array layout. The most important contribution to overall
performance by the system memory controller is to minimize the latency required to initiate and
complete requests to memory and to support the highest possible bandwidth (full streaming, quick
turn-arounds). One measure of performance is the total flight time to complete a cache line
request. A complete discussion of performance involves the entire chipset, not just the system
memory controller.
5.2.4.1
Data Integrity (ECC)
The MCH supports single-bit Error Correcting Code (or Error Checking and Correcting) and
multiple-bit EC (Error Checking) on the system memory interface. The MCH generates an 8-bit
code word for each 64-bit QWord of memory. The MCH performs two QWord writes at a time;
thus, two 8-bit codes are sent with each write. Since the code word covers a full QWord, writes of
less than a QWord require a read-merge-write operation. Consider a DWord write to memory. In
this case, when in ECC mode, the MCH reads the QWord where the addressed DWord will be
written, merges in the new DWord, generates a code covering the new QWord, and, finally, writes
the entire QWord and code back to memory. Any correctable (single-bit) errors detected during
the initial QWord read are corrected before merging the new DWord.
The MCH also supports EC (Error Checking) data integrity mode. In this mode, the MCH
generates and stores a code for each QWord of memory. It then checks the code for reads from
memory but does not correct any errors that are found. Thus, the read performance hit associated
with ECC is not incurred.
5.3
AGP Interface Overview
The MCH supports 1.5 V AGP 1x/2x/4x devices. The AGP signal buffers are 1.5 V drive/receive
(buffers are not 3.3 volt tolerant). The MCH supports 2x/4x source synchronous clocking transfers
for read and write data, and sideband addressing. The MCH also support 2x and 4x clocking for
Fast Writes initiated from the MCH (on behalf of the processor).
AGP PIPE# or SBA[7:0] transactions to system memory do not get snooped and are, therefore, not
coherent with the processor caches. AGP FRAME# transactions to system memory are snooped.
AGP PIPE# and SBA[7:0] accesses to and from the hub interface are not supported. AGP
FRAME# access from an AGP master to the hub interface are also not supported. Only the AGP
FRAME memory writes from the hub interface are supported.
5.3.1
AGP Target Operations
As an initiator, the MCH does not initiate cycles using AGP enhanced protocols. The MCH
supports AGP cycles targeting the interface to system memory only. The MCH supports
interleaved AGP PIPE# and AGP FRAME#, or AGP SBA[7:0] and AGP FRAME# transactions.
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®
Table 15. AGP Commands Supported by the Intel MCH When Acting as an AGP Target
AGP
Command
C/BE[3:0]#
Encoding
MCH Host Bridge
Cycle Destination
Read
Response as PCIx Target
0000
System memory
Low-priority read
0000
Hub interface
Complete with random data
0001
System memory
High-priority read
0000
The Hub interface
Complete with random data
Reserved
0010
N/A
No response
Reserved
0011
N/A
No response
Write
0100
System memory
Low-priority write
0100
Hub interface
Cycle goes to DRAM with byte
enables inactive
0101
System memory
High-priority write
0101
Hub interface
Cycle goes to DRAM with byte
enables inactive; does not go to
the hub interface
Reserved
0110
N/A
No response
Reserved
0111
N/A
No response
Long Read
1000
System memory
Low-priority read
Hub interface
Complete locally with random data;
does not go to the hub interface
System memory
High-priority read
Hub interface
Complete with random data
Hi-Priority Read
Hi-Priority Write
Hi-Priority Long
Read
1001
Flush
1010
MCH
Complete with QW of random data
Reserved
1011
N/A
No response
Fence
1100
MCH
No response; Flag inserted in
MCH request queue
Reserved
1101
N/A
No response
Reserved
1110
N/A
No response
Reserved
1111
N/A
No response
NOTES:
1. N/A refers to a function that is not applicable
As a target of an AGP cycle, the MCH supports all the transactions targeting system memory
(summarized in Table 15). The MCH supports both normal and high-priority read and write
requests. The MCH does not support AGP cycles to the hub interface. PIPE# and SBA cycles do
not require coherency management and all AGP initiator accesses to system memory, using AGP
PIPE# or SBA protocol, are treated as non-snoopable cycles. These accesses are directed to the
AGP aperture in system memory that is programmed as either uncacheable (UC) memory or write
combining (WC) in the processor’s MTRRs.
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5.3.2
AGP Transaction Ordering
The MCH observes transaction ordering rules as defined by the AGP Interface Specification,
Revision 2.0.
5.3.3
AGP Signal Levels
The 4x data transfers use 1.5 V signaling levels as described by the AGP Interface Specification,
Revision 2.0. The MCH supports 1x/2x data transfers using 1.5 V signaling levels.
5.3.4
4x AGP Protocol
In addition to the 1x and 2x AGP protocol, the MCH supports 4x AGP read and write data
transfers and 4x sideband address generation. The 4x operation is compliant with the AGP
Interface Specification, Revision 2.0.
The MCH indicates that it supports 4x data transfers via bit 2 of the AGPSTAT.RATE field.
When bit 2 of the AGPCMD.DRATE field is set to 1 during system initialization, the MCH
performs AGP read/write data transactions using 4x protocol. This bit is not dynamic. Once this
bit is set during initialization, the data transfer rate must not be changed.
The 4x data rate transfer provides 1.06 GB/s transfer rates. The control signal protocol for the 4x
data transfer protocol is identical to 1x/2x protocol. In 4x mode 16 bytes of data are transferred on
every 66 MHz clock edge. The minimum throttleable block size remains four 66 MHz clocks
(64 bytes of data are transferred per block). Three additional signal pins are required to implement
the 4x data transfer protocol. These signal pins are complimentary data transfer strobes for the AD
bus (2) and the SBA bus (1).
5.3.5
Fast Writes
The MCH supports 2x and 4x Fast Writes from the MCH to the graphics controller on AGP. Fast
Write operation is compliant with Fast Writes as currently described in the AGP Interface
Specification, Revision 2.0. To use the Fast Write protocol, both AGPCTRL.FWCE and
AGPCMD.FWPE must be set to 1.
AGPCTRL.FWCE is set to 0 by default. When this bit is set to 1, the MCH indicates that it
supports Fast Writes through AGPSTAT.FW. When both AGPCMD.FWEN and
AGPCTRL.FWCE are set to 1, the MCH uses Fast Write protocol to transfer memory write data to
the AGP master.
Memory writes originating from the processor or from the hub interface use the Fast Write
protocol when it is both capability enabled and enabled. The data rate used to perform the Fast
Writes is dependent on the bits set in the AGPCMD.DRATE field (bits [2:0]). If bit 2 of the
AGPCMD.DRATE field is 1, the data transfers occur using 4x strobing. If bit 1 of
AGPCMD.DRATE field is 1, the data transfers occur using 2x strobing. If bit 0 of
AGPCMD.DRATE field is 1, Fast Writes are disabled and data transfers occur using standard PCI
protocol. Note that only one of the three DRATE bits can be set by initialization software
(Table 16).
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Table 16. Data Rate Control Bits
5.3.6
AGPCNTL
.FWCE
AGPCMD.
FWPE
AGPCMD.
DRATE
[bit 2]
AGPCMD.
DRATE
[bit 1]
AGPCMD.
DRATE
[bit 0]
MCH =>AGP Master Write
Protocol
0
0
X
X
X
1x
1
1
0
0
1
1x
1
1
0
1
0
2x strobing
1
1
1
0
0
4x strobing
AGP FRAME# Transactions on AGP
The MCH accepts and generates AGP FRAME# transactions on the AGP bus. The MCH
guarantees that AGP FRAME# accesses to system memory are kept coherent with the processor
caches by generating snoops to the host bus. LOCK#, SERR#, and PERR# signals are not
supported.
MCH Initiator and Target Operations
Table 17 summarizes MCH target operation for AGP FRAME# initiators. The cycles can be either
destined to system memory or the hub interface.
®
Table 17. PCI Commands Supported by the Intel MCH (When Acting as a FRAME# Target)
PCI Command
Encoding
Cycle Destination
Response as a FRAME#
Target
Interrupt Acknowledge
0000
N/A
No response
Special cycle
0001
N/A
No response
I/O Read
0010
N/A
No response
I/O Write
0011
N/A
No response
Reserved
0100
N/A
No response
Reserved
0101
N/A
No response
Memory Read
0110
System memory
Read
0110
Hub interface
No response
0111
System memory
Posts data
0111
Hub interface
No response
Reserved
1000
N/A
No response
Reserved
1001
N/A
No response
Configuration Read
1010
N/A
No response
Configuration Write
1011
N/A
No response
Memory Read Multiple
1100
System memory
Read
1100
Hub interface
No response
Memory Write
®
Intel® MCH
C/BE[3:0]#
Intel 82845 MCH for SDR Datasheet
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Functional Description
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PCI Command
Dual Address Cycle
Memory Read Line
Memory Write and
Invalidate
Intel® MCH
C/BE[3:0]#
Encoding
Cycle Destination
Response as a FRAME#
Target
1101
N/A
No response
1110
System Memory
Read
1110
Hub interface
No response
1111
System memory
Posts data
1111
Hub interface
Posts Data
NOTES:
1. N/A refers to a function that is not applicable
As a target of an AGP FRAME# cycle, the MCH only supports the following transactions:
• Memory Read, Memory Read Line, and Memory Read Multiple. These commands are
supported identically by the MCH. The MCH does not support reads of the hub interface bus
from AGP.
• Memory Write and Memory Write and Invalidate. These commands are aliased and processed
identically.
• Other Commands. Other commands (e.g., I/O R/W and Configuration R/W) are not supported
by the MCH as a target and result in master abort.
• Exclusive Access. The MCH does not support PCI locked cycles as a target.
• Fast Back-to-Back Transactions. The MCH, as a target, supports fast back-to-back cycles
from an AGP FRAME# initiator.
As an initiator of AGP FRAME# cycle, the MCH only supports the following transactions:
• Memory Read and Memory Read Line. MCH supports reads from host to AGP. MCH does
not support reads from the hub interface to AGP.
• Memory Read Multiple. This command is not supported by the MCH as an AGP FRAME#
initiator.
• Memory Write. The MCH initiates AGP FRAME# cycles on behalf of the host or the hub
interface. As an initiator, the MCH does not issue Memory Write and Invalidate cycles. The
MCH does not support write merging or write collapsing. The MCH allows non-snoopable
write transactions from the hub interface to the AGP bus.
• I/O Read and Write. I/O read and write cycles from the host are sent to the AGP bus. The I/O
base and limit address range for the AGP bus are programmed in the configuration registers.
All other accesses that do not correspond to this programmed address range are forwarded to
the hub interface.
• Exclusive Access. The MCH does not issue a locked cycle on the AGP bus on behalf of either
the host or the hub interface. The hub interface and host locked transactions to AGP are
initiated as unlocked transactions by the MCH on the AGP bus.
• Configuration Read and Write. Host configuration cycles to AGP are forwarded as Type 1
configuration cycles.
• Fast Back-to-Back Transactions. The MCH, as an initiator, does not perform fast back-toback cycles.
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MCH Retry/Disconnect Conditions
The MCH generates retry/disconnect according to the AGP Interface Specification, Revision 2.0
rules when being accessed as a target from the AGP FRAME# device.
Delayed Transaction
When an AGP FRAME#-to-system memory read cycle is retried by the MCH, it is processed
internally as a delayed transaction. The MCH supports the delayed transaction mechanism on the
AGP target interface for the transactions issued using AGP FRAME# protocol. This mechanism is
compatible with the PCI Local Bus Specification, Revision 2.1. The process of latching all
information required to complete the transaction, terminating with Retry, and completing the
request without holding the master in wait-states is called a delayed transaction.
The MCH latches the address and command when establishing a delayed transaction. The MCH
generates a delayed transaction on the AGP only for AGP FRAME# to system memory read
accesses. The MCH does not allow more than one delayed transaction access from AGP at any
time.
5.4
Power and Thermal Management
An 845 chipset platform is compliant with the following specifications:
• APM, Revision 1.2
• ACPI, Revision 1.0b
• PCI Power Management, Revision 1.0
• PC ’99, Revision 1.0
• PC ’99A
• PC ’01, Revision 1.0
5.4.1
Processor Power State Control
• C0 (Full On): This is the only state that runs software. All clocks are running, STPCLK# is
deasserted, and the processor core is active. The processor can service snoops and maintain cache
coherency in this state.
• Stop-Grant State: This function can be enabled or disabled via a configuration bit. When this function
is enabled, STPCLK# is asserted to place the processor into the C2 state with a programmable
duty cycle. This is an ACPI defined function but BIOS or APM (via BIOS) can use this
facility.
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Functional Description
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5.4.2
Sleep State Control
• S0 (Awake): In this state all power planes are active. All of the ACPI software “C” states are
embedded in this state.
• S1: The recommended implementation of S1 state is the same as C2 state (Stop Grant), which
is entered by the assertion of the STPCLK# signal from the ICH2 to the processor. A further
power saving can be achieved by asserting processor SLP# from the ICH2. This puts the
processor into Sleep State.
• S2: ACPI S2 state is not supported in the 845 chipset desktop platform.
• S3 (Suspend To RAM (STR)): The next level of power reduction occurs when the clock
synthesizers and main power planes (ICH2, MCH, and the processor) are shut down but the
system memory plane and the ICH2 resume well remain active. This is the Suspend-to-RAM
(STR) state. All clocks from synthesizers are shut down during the S3 state.
• S4 and S5 (Suspend To Disk (STD), Soft Off): The next level of power reduction occurs
when the memory power and MCH are shut down in addition to the clock synthesizers, ICH2,
and the processor power planes. The ICH2 resume well is still powered.
• G3 (Mechanical Off): In this state only the RTC well is powered. The system can only
reactivate when the power switch is returned to the “On” position.
5.5
Intel® MCH Clocking
The 845 chipset is supported by the CK_408 compliant clock synthesizer. For details on clocking,
refer to the Intel® Pentium 4 Processor in a 478 Pin Package and Intel® 845 Chipset Platform
Design Guide.
5.6
Intel® MCH System Reset and Power Sequencing
For details on MCH system reset and power sequencing, refer to the Intel® Pentium 4 Processor in
a 478 Pin Package and Intel® 845 Chipset Platform Design Guide.
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6
Electrical Characteristics
This chapter contains the absolute maximum operating ratings, power characteristics, and DC
characteristics for the 82845 MCH.
6.1
Absolute Maximum Ratings
Table 18 lists the MCH’s maximum environmental stress ratings. Functional operation at the
absolute maximum and minimum is neither implied nor guaranteed. Functional operating
parameters are listed in the DC tables.
Warning: Stressing the device beyond the “Absolute Maximum Ratings” may cause permanent damage.
These are stress ratings only. Operating beyond the “operating conditions” is not recommended
and extended exposure beyond “operating conditions” may affect reliability.
Table 18. Absolute Maximum Ratings
Symbol
6.2
Parameter
Min
Max
Unit
-55
150
°C
Tstorage
Storage Temperature
VCC1_5
1.5 V Supply Voltage with respect to VSS
-0.72
2.3
V
VCC1_8
1.8 V Supply Voltage with respect to VSS
-0.88
2.69
V
VCCSM
3.3 V Supply Voltage with respect to VSS
-2.83
6.3
V
VTT
AGTL+ buffer DC input voltage with respect
to VSS
-0.55
2.3
V
Notes
Power Characteristics
Table 19. Power Characteristics
Symbol
Parameter
Min
Typ
Max
Unit
Notes
IVTT
MCH VTT supply current
2.4
A
IVCC1_5_CORE
1.5 V core supply current
1.5
A
1
IVCC1_5_AGP
1.5 V AGP supply current
0.37
A
1
IVCC1_8
1.8 V hub interface supply current
0.20
A
IVCCSM
3.3 V system memory supply current
2.0
A
ISUS_3.3
3.3 V standby supply current
25
mA
HVREF, AGPREF, HI_REF, SDREF
supply current
10
mA
NOTES:
1. These current levels can happen simultaneously, and can be summed into one supply.
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Intel 82845 MCH for SDR Datasheet
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Electrical Characteristics
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6.3
Signal Groups
The signal description includes the type of buffer used for the particular signal:
AGTL+
Open Drain AGTL+ interface signal. Refer to the AGTL+ I/O Specification for
complete details. The MCH integrates most AGTL+ termination resistors.
AGP
AGP interface signals. These signals are compatible with AGP 2.0 1.5 V
Signaling Environment DC and AC Specifications. The buffers are not 3.3 V
tolerant.
HI CMOS
Hub Interface 1.8 V CMOS buffers.
SM CMOS
System memory 3.3 V CMOS buffers.
Table 20. Signal Groups
Signal
Group
120
Signal Type
Signals
(a)
AGTL+ I/O
ADS#, BNR#, BR0#,DBSY#, DBI[3:0]#, DRDY#, HA[31:3]#,
HADSTB[1:0] #, HD[63:0]#, HDSTBP[3:0]#, HDSTBN[3:0]#, HIT#,
HITM#, HREQ[4:0]#
(b)
AGTL+ Output
BPRI#, CPURST#, DEFER#, HTRDY#, RS[2:0]#
(c)
AGTL+ Input
HLOCK#
(d)
Host Reference
Voltages
HVREF, HSWING[1:0]
(e)
AGP I/O
AD_STB0, AD_STB0#, AD_STB1, AD_STB1#, G_FRAME#,
G_IRDY#, G_TRDY#, G_STOP#, G_DEVSEL#, G_AD[31:0],
G_C/BE[3:0]#, G_PAR
(f)
AGP Input
PIPE#, SBA[7:0], RBF#, WBF#, SB_STB, SB_STB#, G_REQ#
(g)
AGP Output
ST[2:0], G_GNT#
(h)
AGP Reference
Voltage
AGPREF
(i)
Hub Interface’s
CMOS I/O
HI_[10:0], HI_STB, HI_STB#
(j)
Hub Interface
Reference Voltage
HI_REF
(k)
SDRAM CMOS I/O
SDQ[63:0], SCB[7:0]
(l)
SDRAM CMOS
Output
SCS[11:0]#, SMA[12:0], SBS[1:0], SRAS#, SCAS#, SWE#,
SCKE[5:0], SCK[11:0], RDCLKO
(m)
SDRAM CMOS Input
RDCLKI
(n)
SDRAM Reference
Voltage
SDREF
(o)
CMOS Input
TESTIN#
(p)
CMOS Input
RSTIN# (3.3V)
(r)
AGTL+ Termination
Voltage
VTT
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Intel 82845 MCH for SDR Datasheet
Electrical Characteristics
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®
Signal
Group
Signal Type
(s)
1.5 V Core and AGP
Voltage
VCC1_5
(t)
1.8 V Hub Interface
Voltage
VCC1_8
(u)
3.3 V PC133
SDRAM I/O Voltage
VCCSM
(v)
CMOS Clock Input
66IN
(w)
CMOS Clock Input
BCLK, BCLK#
Intel 82845 MCH for SDR Datasheet
Signals
121
Electrical Characteristics
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6.4
DC Characteristics
Table 21. DC Characteristics
Symbol
Signal
Group
Parameter
Min
Typ
Max
Unit
Notes
I/O Buffer Supply Voltage
VCCSM
(u)
PC133 SDRAM I/O Voltage
3.135
3.3
3.465
V
VCC1_8
(t)
1.8V I/O Supply Voltage
1.71
1.8
1.89
V
VCC1_5
(s)
Core and AGP Voltage
1.425
1.5
1.575
V
VTT
(r)
Host AGTL+ Termination Voltage
N/A
1.75
V
N/A
Reference Voltages
HVREF
(d)
Host Address and Data Reference
Voltage
(2/3 x VTT) – 2%
2/3 x VTT
(2/3 x VTT) + 2%
V
HSWING
(d)
Host Compensation Reference
Voltage
(1/3 x VTT) – 2%
1/3 x VTT
(1/3 x VTT) + 2%
V
HI_REF
(j)
Hub Interface Reference Voltage
0.48 x VCC1_8
1/2 x VCC1_8
0.52 x VCC1_8
V
SDREF
(n)
SDRAM Reference Voltage
0.49 x VCCSM
1/2 x VCCSM
0.51 x VCCSM
V
AGPREF
(h)
AGP Reference Voltage
0.48 x VCC1_5
1/2 x VCC1_5
0.52 x VCC1_5
V
(2/3 x VTT) – 0.1
V
System Bus Interface
VIL
(a,c)
Host AGTL+ Input Low Voltage
VIH
(a,c)
Host AGTL+ Input High Voltage
VOL
(a,b)
Host AGTL+ Output Low Voltage
VOH
(a,b)
Host AGTL+ Output High Voltage
IOL
(a,b)
Host AGTL+ Output Low Current
ILEAK
(a,c)
Host AGTL+ Input Leakage
Current
CPAD
(a,c)
Host AGTL+ Input Capacitance
(2/3 x VTT) + 0.1
V
(1/3 x VTT) + 0.1
VTT-0.1
V
V
VTTmax / 0.75Rtt
mA
Rttmin = 45 Ω
Rtttyp = 50 Ω
Rttmax = 55 Ω
±15
µA
VOL<Vpad<
VTT
1.0
pF
3.3 V Interface
VIL
(k,m,p)
Input Low Voltage
VIH
(k,m,p)
Input High Voltage
VOL
(k,l)
Output Low Voltage
VOH
(k,l)
Output High Voltage
IOL
(k,l)
Output Low Current
IOH
(k,l)
Output High Current
ILEAK
(k,m,p)
122
SDREF – 2.0
SDREF + 2.0
V
V
0.4
2.4
V
V
4
-4
±100
Input Leakage Current
®
mA
@VOL_S max
mA
@VOH_S max
µA
0<Vin<VCC3_3
Intel 82845 MCH for SDR Datasheet
Electrical Characteristics
R
Symbol
Signal
Group
CI/0
(k,m,p)
Parameter
Input Capacitance
Min
Typ
4.65
Max
Unit
5.37
pF
0.4 x VCC1_5
V
Notes
1.5 V Interface
VIL
(e,f)
Input Low Voltage
VIH
(e,f)
Input High Voltage
VOL
(e,g)
Output Low Voltage
VOH
(e,g)
Output High Voltage
IOL
(e,g)
Output Low Current
IOH
(e,g)
Output High Current
ILEAK
(e,f)
Input Leakage Current
CIN
(e,f)
Input Capacitance
0.6 x VCC1_5
V
0.15 x VCC1_5
0.85 x VCC1_5
V
V
1
mA
@VOL_A max
mA
@VOH_A max
±15
µA
0<Vin<VCC1_5
1.92
pF
HI_REF – 0.15
V
-0.2
1.32
1.8 V Interface
VIL
(i,o)
Input Low Voltage
VIH
(i,o)
Input High Voltage
VOL
(i,o)
Output Low Voltage
VOH
(i,o)
Output High Voltage
IOL
(i,o)
Output Low Current
IOH
(i,o)
Output High Current
ILEAK
(i,o)
Input Leakage Current
CIN
(i,o)
Input Capacitance
VIL
(v)
Input Low Voltage
VIH
(v)
Input High Voltage
2.4
CIN
(v)
Input Capacitance
1.2
VIL
(w)
Input Low Voltage
VIH
(w)
Input High Voltage
0.660
VCROSS
(w)
Crossing Voltage
0.45 x (VIH – VIL)
CIN
(w)
Input Capacitance
0.94
HI_REF + 0.15
V
0.1 x VCC1_8
0.9 x VCC1_8
1
IOL= 1 mA
V
IOH = 1 mA
mA
@VOL_HI max
mA
@VOH_HI max
-150, +15
µA
0<Vin<VCC1_8
3.17
pF
0.8
V
-1
2.58
V
Clock Signals
V
1.4
0
0.710
pF
V
0.850
0.5 x (VIH – VIL) 0.55 x (VIH – VIL)
V
V
1.1
pF
0.8
V
RSTIN# Signals
VIL
(p)
Input Low Voltage
VIH
(p)
Input High Voltage
ILEAK
(p)
Input Leakage Current
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Intel 82845 MCH for SDR Datasheet
2.0
V
±100
µA
0<Vin<VCC3_3
123
Electrical Characteristics
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Ballout and Package Information
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7
Ballout and Package Information
This chapter provides the MCH ballout and package information. The ballout footprint is shown in
Figure 6 and Figure 7. These figures represent the ballout organized by ball number. Table 22
provides the MCH ballout listed alphabetically by signal name.
The following notes apply to the ballout.
Note: NC = No Connect.
Note: RSVD = These pins should not be connected and should be allowed to float.
Note: VSS = Connect to ground.
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Intel 82845 MCH for SDR Datasheet
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Ballout and Package Information
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®
Figure 6. Intel 82845 MCH Ballout Diagram (Top View—Left Side)
29
28
AJ
AH
AG
VCC1_5
VSS
VCC1_5
VSS
VCC1_5
VSS
VCC1_5
VSS
VCC1_8
VSS
VCCSM
VSS
VCCSM
B
VSS
HD61#
HD57#
SBA2
SBA3
ST2
ST0
G_REQ#
VTT
VSS
VTT
VSS
VTT
VSS
HD56#
HD55#
HD54#
SB_STB
SB_STB#
VSS
ST1
VCC1_5
PIPE#
VSS
VTT
VSS
VTT
VSS
HD59#
VSS
SBA5
VCC1_5
SBA7
SBA6
WBF#
RBF#
VTT
VSS
VTT
VSS
CPURST#
HD63#
HD60#
NC
NC
GRCOMP
G_AD31
VCC1_5
VSS
VCC1_5
VTT
VSS
VTT
HD62#
VSS
DBI3#
AD_STB1
VSS
G_AD28
G_AD29
VSS
G_AD30
VSS
VSS
VTT
VSS
HD58#
G_AD20
G_AD22
G_AD19
G_AD27
G_AD24
VSS
VCC1_5
VTT
VSS
VTT
HVREF
VSS
VSS
G_AD21
VCC1_5
G_AD26
G_AD25
G_C/BE3#
VCC1_5
AGPREF
G_AD16
G_AD17
G_AD23
VSS
G_IRDY#
VSS
G_PAR
G_TRDY#
G_STOP#
VCC1_5
G_AD9
G_AD8
G_C/BE0#
G_AD15
G_C/BE1#
VSS
G_AD6
VCC1_5
G_AD14
G_AD13
G_AD11
VCC1_5
VSSA1
VCC1_5
VSS
G_AD5
G_AD4
G_AD2
G_AD12
G_AD10
VSS
VCCA1
VSS
VCC1_5
G_AD0
VSS
G_AD3
AD_STB0
AD_STB0#
VCC1_5
VSS
VCC1_5
VSS
HLRCOMP
HI_REF
HI_0
HI_1
HI_3
66IN
VCC1_5
VSS
VCC1_5
HI_2
VCC1_8
HI_STB
HI_STB#
VCC1_8
VSS
VSS
VCC1_5
VSS
HI_8
HI_4
HI_5
HI_10
VSS
VCC1_8
HI_7
VSS
VCC1_8
VSS
VCCSM
VSS
VSS
VCCSM
RSVD
VCCSM
RSVD
VCCSM
RSTIN#
VSS
SCAS#
SCS4#
SCS1#
VSS
SDREF
RSVD
TESTIN#
SCS9#
VCCSM
SCS0#
VCCSM
VSS
VCCSM
VSS
VCCSM
VSS
VCCSM
VSS
SWE#
VSS
SCS8#
SCS5#
SRAS#
SMA0
SMA3
SMA5
SMA8
SMA9
SBS1
SCK8
SCK4
SDQ0
RSVD
SDQ37
VSS
SDQ8
VCCSM
SMA2
VSS
SMA7
VCCSM
SBS0
VSS
SCK9
SDQ1
VSS
SDQ5
SDQ39
SDQ41
SDQ43
SMA1
SMA4
SMA6
SDQ47
SMA10
SCB1
SMA11
SDQ35
SDQ4
VCCSM
SDQ7
VCCSM
SDQ42
VSS
SDQ12
VCCSM
SDQ46
VSS
SCB5
VCCSM
SDQ34
SDQ3
RSVD
SDQ38
SDQ40
RSVD
SDQ10
SDQ11
SDQ45
SDQ13
SDQ14
SDQ15
SCB0
SCB2
SDQ2
SDQ36
SDQ6
SDQ9
SDQ44
RSVD
SCB4
SCB6
VSS
VCCSM
VSS
VCCSM
VSS
VCCSM
VSS
SBA4
AD_STB1#
G_AD18
G_DEVSEL#
G_AD7
G_AD1
HI_9
HI_6
SMRCOMP
SDQ32
SDQ33
A
29
15
VSS
D
C
16
VSS
F
E
17
G_GNT#
H
G
18
SBA1
K
J
19
SBA0
M
L
20
VSS
P
N
21
VSS
T
R
22
VTT
V
U
23
VTT
Y
W
24
VTT
AB
AA
25
VCC1_5
AD
AC
26
VSS
AF
AE
27
28
27
26
G_C/BE2# G_FRAME#
25
24
23
22
21
20
19
18
17
HDSTBP3# HDSTBN3#
16
15
NOTES:
1.
NC = No Connect.
2.
RSVD = These pins should not be connected and should be allowed to float.
3.
VSS = Connect to ground.
126
®
Intel 82845 MCH for SDR Datasheet
Ballout and Package Information
R
®
Figure 7. Intel 82845 MCH Ballout Diagram (Top View—Right Side)
14
13
12
11
10
9
8
7
6
5
4
3
2
AJ
VSS
VSS
VSS
VSS
VSS
VSS
HD49#
HD44#
DBI2#
HD24#
HD31#
HD25#
HD20#
HD17#
HD52#
HD48#
HD45#
HD42#
HD43#
HD38#
HD27#
HD28#
HD29#
HD16#
DBI1#
HD22#
HD51#
VSS
HD47#
VSS
HD41#
VSS
HD30#
VSS
HD19#
VSS
HD26#
HD21#
HD53#
HD46#
HD40#
HDSTBN2#
HD36#
HD34#
HD18#
HD23#
VSS
HD8#
VSS
HSWNG1
VSS
HDSTBP2#
VSS
HD37#
VSS
HD10#
VSS
DBI0#
HD50#
HRCOMP1
HD33#
HD32#
HD39#
HD35#
HD14#
HD11#
HD12#
HD5#
VSS
HD13#
VSS
VSS
VSS
HVREF
VSS
VSS
VTT
HD9#
VSS
HD1#
HD4#
HD3#
VTT
VSS
HSWNG0
HD7#
HD2#
VSS
HD6#
HVREF
BPRI#
VSS
HIT#
DEFER#
HITM#
VSS
RS1#
RS2#
HLOCK#
VSS
BNR#
VSS
BR0#
VSS
DBSY#
DRDY#
ADS#
HDSTBP1# HDSTBN1#
VSSA0
VTT
HTRDY#
HREQ0#
HREQ3#
VSS
HA6#
VSS
VCCA0
VSS
HREQ1#
VSS
HA4#
HA3#
HA5#
VCC1_5
VSS
HVREF
HREQ2#
HA11#
HADSTB0#
VSS
HA7#
VSS
VCC1_5
VSS
HA8#
VSS
HA12#
HA10#
HA13#
VCC1_5
VSS
VSS
HA15#
HADSTB1#
HA28#
VSS
HA16#
VTT
HVREF
HA30#
HA24#
HA18#
HA19#
VSS
HA31#
VSS
HA21#
VSS
HA20#
BCLK#
VSS
VCCSM
VSS
HA17#
HA22#
SDREF
BCLK
VCCSM
VSS
VCCSM
VSS
HA25#
HD15#
HRCOMP0
HD0#
RS0#
HREQ4#
HA9#
HA14#
HA26#
HA23#
HA27#
RDCLKO
SCK5
SCK1
SMA12
SCKE4
SCKE2
SCKE0
SCS3#
SCS2#
SCS10#
SCK11
VCCSM
RDCLKIN
VCCSM
SCK0
VSS
SDQ51
VCCSM
SDQ22
VSS
SCS7#
VCCSM
SCKE3
SCKE1
SCK6
SDQ48
SDQ17
SDQ50
SDQ20
SDQ53
SDQ56
SDQ24
SDQ25
SDQ59
SCKE5
VSS
SCK7
SCB3
VSS
RSVD
VCCSM
SDQ54
VSS
SDQ57
VCCSM
SDQ27
VSS
SDQ29
SDQ63
SCB7
SDQ49
SDQ18
SDQ52
SDQ21
SDQ23
RSVD
SDQ26
SDQ60
RSVD
SDQ61
SDQ30
SCK3
SDQ31
VSS
VCCSM
VSS
VCCSM
VSS
10
9
8
7
6
5
4
3
W
VSS
U
VSS
R
VSS
N
VSS
L
VSS
J
H
SCK10
VCCSM
VSS
K
SCS11#
SDQ62
AA
M
SCS6#
SDQ28
VSS
P
VCCSM
SDQ58
AC
T
VSS
SDQ55
VSS
V
VCCSM
SDQ19
AE
Y
VSS
11
VSS
AB
VCCSM
SDQ16
AG
AD
VSS
12
VSS
AF
VCCSM
13
AH
HDSTBN0# HDSTBP0#
VCC1_5
14
1
HA29#
VCCSM
G
F
SCK2
VSS
E
D
VCCSM
C
B
A
2
1
NOTES:
1.
NC = No Connect.
2.
RSVD = These pins should not be connected and should be allowed to float.
3.
VSS = Connect to ground.
®
Intel 82845 MCH for SDR Datasheet
127
Ballout and Package Information
R
®
Table 22. Intel 82845 MCH Ballout Listed Alphabetically by Signal Name
Signal Name
128
Ball #
Signal Name
Ball #
66IN
P22
G_AD14
U25
AD_STB0
R24
G_AD15
V24
AD_STB0#
R23
G_AD16
Y27
AD_STB1
AC27
G_AD17
Y26
AD_STB1#
AC28
G_AD18
AA28
ADS#
V3
G_AD19
AB25
AGPREF
AA21
G_AD20
AB27
BCLK#
K8
G_AD21
AA27
BCLK
J8
G_AD22
AB26
BNR#
W3
G_AD23
Y23
BPRI#
Y7
G_AD24
AB23
BR0#
V7
G_AD25
AA24
CPURST#
AE17
G_AD26
AA25
DBSY#
V5
G_AD27
AB24
DEFER#
Y4
G_AD28
AC25
DBI0#
AD5
G_AD29
AC24
DBI1#
AG4
G_AD30
AC22
DBI2#
AH9
G_AD31
AD24
DBI3#
AD15
G_C/BE0#
V25
DRDY#
V4
G_C/BE1#
V23
G_AD0
R27
G_C/BE2#
Y25
G_AD1
R28
G_C/BE3#
AA23
G_AD2
T25
G_DEVSEL#
W28
G_AD3
R25
G_FRAME#
Y24
G_AD4
T26
G_GNT#
AH25
G_AD5
T27
G_IRDY#
W27
G_AD6
U27
G_PAR
W25
G_AD7
U28
G_REQ#
AG24
G_AD8
V26
G_STOP#
W23
G_AD9
V27
G_TRDY#
W24
G_AD10
T23
GRCOMP
AD25
G_AD11
U23
HA3#
T4
G_AD12
T24
HA4#
T5
G_AD13
U24
HA5#
T3
®
Intel 82845 MCH for SDR Datasheet
Ballout and Package Information
R
Signal Name
®
Ball #
Signal Name
Ball #
HA6#
U3
HD8#
AE3
HA7#
R3
HD9#
AB7
HA8#
P7
HD10#
AD7
HA9#
R2
HD11#
AC7
HA10#
P4
HD12#
AC6
HA11#
R6
HD13#
AC3
HA12#
P5
HD14#
AC8
HA13#
P3
HD15#
AE2
HA14#
N2
HD16#
AG5
HA15#
N7
HD17#
AG2
HA16#
N3
HD18#
AE8
HA17#
K4
HD19#
AF6
HA18#
M4
HD20#
AH2
HA19#
M3
HD21#
AF3
HA20#
L3
HD22#
AG3
HA21#
L5
HD23#
AE5
HA22#
K3
HD24#
AH7
HA23#
J2
HD25#
AH3
HA24#
M5
HD26#
AF4
HA25#
J3
HD27#
AG8
HA26#
L2
HD28#
AG7
HA27#
H4
HD29#
AG6
HA28#
N5
HD30#
AF8
HA29#
G2
HD31#
AH5
HA30#
M6
HD32#
AC11
HA31#
L7
HD33#
AC12
HADSTB0#
R5
HD34#
AE9
HADSTB1#
N6
HD35#
AC9
HD0#
AA2
HD36#
AE10
HD1#
AB5
HD37#
AD9
HD2#
AA5
HD38#
AG9
HD3#
AB3
HD39#
AC10
HD4#
AB4
HD40#
AE12
HD5#
AC5
HD41#
AF10
HD6#
AA3
HD42#
AG11
HD7#
AA6
HD43#
AG10
Intel 82845 MCH for SDR Datasheet
129
Ballout and Package Information
R
Signal Name
130
Ball #
Signal Name
Ball #
HD44#
AH11
HI_8
M27
HD45#
AG12
HI_9
N28
HD46#
AE13
HI_10
M24
HD47#
AF12
HI_REF
P26
HD48#
AG13
HI_STB
N25
HD49#
AH13
HI_STB#
N24
HD50#
AC14
HIT#
Y5
HD51#
AF14
HITM#
Y3
HD52#
AG14
HLOCK#
W5
HD53#
AE14
HLRCOMP
P27
HD54#
AG15
HRCOMP0
AC2
HD55#
AG16
HRCOMP1
AC13
HD56#
AG17
HREQ0#
U6
HD57#
AH15
HREQ1#
T7
HD58#
AC17
HREQ2#
R7
HD59#
AF16
HREQ3#
U5
HD60#
AE15
HREQ4#
U2
HD61#
AH17
HSWNG0
AA7
HD62#
AD17
HSWNG1
AD13
HD63#
AE16
HTRDY#
U7
HDSTBN0#
AD4
HVREF
M7, R8, Y8, AB11, AB17
HDSTBP0#
AD3
NC
AD26, AD27
HDSTBN1#
AE6
PIPE#
AF22
HDSTBP1#
AE7
RBF#
AE22
HDSTBN2#
AE11
RDCLKIN
G3
HDSTBP2#
AD11
RDCLKO
H3
HDSTBN3#
AC15
RS0#
W2
HDSTBP3#
AC16
RS1#
W7
HI_0
P25
RS2#
W6
HI_1
P24
RSTIN#
J27
HI_2
N27
RSVD
HI_3
P23
B19, C5, C8, C23, C26, D12,
F26, H27, K23, K25
HI_4
M26
SBA0
AH28
HI_5
M25
SBA1
AH27
HI_6
L28
SBA2
AG28
HI_7
L27
SBA3
AG27
®
Intel 82845 MCH for SDR Datasheet
Ballout and Package Information
R
Signal Name
®
Ball #
Signal Name
Ball #
SBA4
AE28
SCS9#
H25
SBA5
AE27
SCS10#
G6
SBA6
AE24
SCS11#
H6
SBA7
AE25
SDQ0
F27
SB_STB
AF27
SDQ1
E27
SB_STB#
AF26
SDQ2
B28
SBS0
F17
SDQ3
C27
SBS1
G17
SDQ4
D26
SCAS#
J25
SDQ5
E25
SCK0
F13
SDQ6
B25
SCK1
G13
SDQ7
D24
SCK2
E2
SDQ8
F23
SCK3
C2
SDQ9
B23
SCK4
G15
SDQ10
C22
SCK5
G14
SDQ11
C21
SCK6
F3
SDQ12
D20
SCK7
E3
SDQ13
C19
SCK8
G16
SDQ14
C18
SCK9
F15
SDQ15
C17
SCK10
H5
SDQ16
B13
SCK11
G5
SDQ17
E13
SCKE0
G9
SDQ18
C12
SCKE1
F4
SDQ19
B11
SCKE2
G10
SDQ20
E11
SCKE3
F5
SDQ21
C10
SCKE4
G11
SDQ22
F9
SCKE5
E5
SDQ23
C9
SCS0#
H23
SDQ24
E8
SCS1#
J23
SDQ25
E7
SCS2#
G7
SDQ26
C7
SCS3#
G8
SDQ27
D6
SCS4#
J24
SDQ28
B5
SCS5#
G24
SDQ29
D4
SCS6#
H7
SDQ30
C3
SCS7#
F7
SDQ31
B2
SCS8#
G25
SDQ32
G28
Intel 82845 MCH for SDR Datasheet
131
Ballout and Package Information
R
Signal Name
132
Ball #
Signal Name
Ball #
SDQ33
E28
SCB5
D16
SDQ34
C28
SCB6
B15
SDQ35
D27
SCB7
C14
SDQ36
B27
SDREF
J9, J21
SDQ37
F25
SMA0
G22
SDQ38
C25
SMA1
E21
SDQ39
E24
SMA2
F21
SDQ40
C24
SMA3
G21
SDQ41
E23
SMA4
E20
SDQ42
D22
SMA5
G20
SDQ43
E22
SMA6
E19
SDQ44
B21
SMA7
F19
SDQ45
C20
SMA8
G19
SDQ46
D18
SMA9
G18
SDQ47
E18
SMA10
E17
SDQ48
E14
SMA11
E15
SDQ49
C13
SMA12
G12
SDQ50
E12
SMRCOMP
J28
SDQ51
F11
SRAS#
G23
SDQ52
C11
ST0
AG25
SDQ53
E10
ST1
AF24
SDQ54
D10
ST2
AG26
SDQ55
B9
SWE#
G27
SDQ56
E9
TESTIN#
H26
SDQ57
D8
VCC1_5
SDQ58
B7
SDQ59
E6
R22, R29, U22, U26, W22,
W29, AA22, AA26, AB21,
AC29, AD21, AD23, AE26,
AF23, AG29, AJ25
SDQ60
C6
VCC1_5
N14, N16, P13, P15, P17,
R14, R16, T15, U14, U16
SDQ61
C4
VCCA1
T17
SDQ62
B3
VCCA0
T13
SDQ63
D3
VCC1_8
L25, L29, M22, N23, N26
SCB0
C16
VCCSM
SCB1
E16
SCB2
C15
SCB3
D14
SCB4
B17
A5, A9, A13, A17, A21, A25,
C1, C29, D7, D11, D15, D19,
D23, D25, F6, F10, F14, F18,
F22, G1, G4, G29, H8, H10,
H12, H14, H16, H18, H20,
H22, H24, J5, J7, K6, K22,
K24, K26, L23
®
Intel 82845 MCH for SDR Datasheet
Ballout and Package Information
R
Signal Name
VSS
®
Ball #
A3, A7, A11, A15, A19, A23,
A27, D5, D9, D13, D17, D21,
E1, E4, E26, E29, F8, F12,
F16, F20, F24, G26, H9, H11,
H13, H15, H17, H19, H21, J1,
J4, J6, J22, J26, J29, K5, K7,
K27, L1, L4, L6, L8, L22, L24,
L26, M23, N1, N4, N8, N13,
N15, N17, N22, N29, P6, P8,
P14, P16, R1, R4, R13, R15,
R17, R26, T6, T8, T14, T16,
T22, U1, U4, U15, U29, V6,
V8, V22, W1, W4, W8, W26,
Y6, Y22, AA1, AA4, AA8,
AA29, AB6, AB9, AB10, AB12,
AB13, AB14, AB15, AB16,
AB19, AB22, AC1, AC4,
AC18, AC20, AC21, AC23,
AC26, AD6, AD8, AD10,
AD12, AD14, AD16, AD19,
AD22, AE1, AE4, AE18, AE20,
AE29, AF5, AF7, AF9, AF11,
AF13, AF15, AF17, AF19,
AF21, AF25, AG1, AG18,
AG20, AG22, AH19, AH21,
AH23, AJ3, AJ5, AJ7, AJ9,
AJ11, AJ13, AJ15, AJ17, AJ27
Intel 82845 MCH for SDR Datasheet
Signal Name
Ball #
VSSA1
U17
VSSA0
U13
VTT
M8, U8, AA9, AB8, AB18,
AB20, AC19, AD18, AD20,
AE19, AE21, AF18, AF20,
AG19, AG21, AG23, AJ19,
AJ21, AJ23
WBF#
AE23
NOTES:
1. NC = No Connect.
2. RSVD = These pins should not be connected
and should be allowed float.
3. VSS = Connect to ground.
133
Ballout and Package Information
R
7.1
Package Mechanical Information
This section provides the MCH package mechanical dimensions. The package is a 593 ball
FC-BGA.
®
Figure 8. Intel MCH FC-BGA Package Dimensions (Top and Side View)
Top View
37.50
33.90
16.95
16.95
37.50
33.90
9.67
0.61
36.28
Side View
Die
Substrate
See D etail A
0.600 ±0.100
1.100 ±0.100
A
Detail A
0.74 ±0.025
0.10 ±0.025
0.152
Underfill
Epoxy
Die Solder
Bum ps
Units = M illim eters
pkg_olga_593_top-side
134
®
Intel 82845 MCH for SDR Datasheet
Ballout and Package Information
R
®
Figure 9. Intel MCH FC-BGA Package Dimensions (Bottom View)
35.560
17.780
1.270
AJ
AH
AG
AF
AE
AD
AC
AB
AA
Y
W
V
U
T
35.560
R
P
N
M
L
K
J
17.780
H
G
F
E
D
1.270
C
B
A
1
2
3
4
5
6
7
8
9
22
28
10 11 12 13 14 15 16 17 18
20
23 24 25 26 27
29
21
19
Note: All dim ensions are in m illim eters
pkg-MC H_olga_593_Bot
®
Intel 82845 MCH for SDR Datasheet
135
Ballout and Package Information
R
This page is intentionally left blank.
136
®
Intel 82845 MCH for SDR Datasheet
Testability
R
8
Testability
In the MCH, testability for Automated Test Equipment (ATE) board-level testing has been
implemented as an XOR chain. An XOR-tree is a chain of XOR gates, each with one input pin
connected to it (see Figure 10).
Figure 10. XOR Tree Chain
VCC1_8
XOR
Out
Input
Input
Input
Input
Input
xor.vsd
The algorithm used for in-circuit test is as follows:
• Drive all input pins to an initial logic level 1. Observe the output corresponding to scan chain
being tested.
• Toggle pins one at a time (starting from the first pin in the chain and continuing to the last
pin) from its initial logic level to the opposite logic level. Observe the output changes with
each pin toggle.
8.1
XOR Test Mode Initialization
XOR test mode can be entered by pulling three shared pins (reset straps) low through the rising
transition of RSTIN#. The signals that need to be pulled are as follows:
• G_GNT# = 0 (Global strap enable)
• SBA1 = 0 (XOR strap)
• ST2 = 0 (PLL Bypass mode; it is recommended to enter PLL Bypass in XOR test mode)
®
Intel 82845 MCH for SDR Datasheet
137
Testability
R
8.2
XOR Chains
Note: RSTIN#, TESTIN#, and all Rcomp buffers are not part of any XOR chain.
Table 23. XOR Chain 0
138
Chain 0 Ball
Element #
Signal Name
Note
Initial Logic
Level
AE6
1
HDSTBP1#
Input
1
AD3
2
HDSTBP0#
Input
1
V3
3
ADS#
Input
1
U6
4
HREQ0#
Input
1
U3
5
HA6#
Input
1
U2
6
HREQ4#
Input
1
U5
7
HREQ3#
Input
1
T5
8
HA4#
Input
1
T7
9
HREQ1#
Input
1
T4
10
HA3#
Input
1
R7
11
HREQ2#
Input
1
R5
12
HADSTB0#
Input
1
R3
13
HA7#
Input
1
P3
14
HA13#
Input
1
R2
15
HA9#
Input
1
R6
16
HA11#
Input
1
T3
17
HA5#
Input
1
N3
18
HA16#
Input
1
P5
19
HA12#
Input
1
P4
20
HA10#
Input
1
P7
21
HA8#
Input
1
N2
23
HA14#
Input
1
N7
24
HA15#
Input
1
N5
25
HA28#
Input
1
M4
26
HA18#
Input
1
L3
27
HA20#
Input
1
M3
28
HA19#
Input
1
L2
29
HA26#
Input
1
K3
30
HA22#
Input
1
®
Intel 82845 MCH for SDR Datasheet
Testability
R
®
Chain 0 Ball
Element #
Signal Name
Note
Initial Logic
Level
M5
31
HA24#
Input
1
K3
32
HA23#
Input
1
K4
33
HA17#
Input
1
J3
34
HA25#
Input
1
L5
35
HA21#
Input
1
H4
36
HA27#
Input
1
M6
37
HA30#
Input
1
L7
38
HA31#
Input
1
G2
39
HA29#
Input
1
H6
40
SCS11#
Input
1
H3
41
RDCLKIN
Input
1
G3
42
RDCLKO
Input
1
H5
43
SCK10
Input
1
G6
44
SCS10#
Input
1
E7
45
SCS7#
Input
1
G8
46
SCS3#
Input
1
G9
47
SCKE0
Input
1
AH28
48
SBA0
Output
N/A
Intel 82845 MCH for SDR Datasheet
139
Testability
R
Table 24. XOR Chain 1
140
Chain 1 Ball
Element #
Signal Name
Note
Initial Logic
Level
N6
1
HADSTDB1#
Input
1
H7
2
SCS6#
Input
1
G10
3
SCKE2
Input
1
G5
4
SCK11
Input
1
F4
5
SCKE1
Input
1
F3
6
SCK6
Input
1
C2
7
SCK3
Input
1
B2
8
SDQ31
Input
1
E2
9
SCK2
Input
1
D3
10
SDQ63
Input
1
E3
11
SCK7
Input
1
G7
12
SCS2#
Input
1
C3
13
SDQ30
Input
1
E5
14
SCKE5
Input
1
F7
15
SCS7#
Input
1
D4
16
SDQ29
Input
1
C4
17
SDQ61
Input
1
C5
18
RSVD
Input
1
E6
19
SDQ59
Input
1
D6
20
SDQ27
Input
1
B3
21
SDQ62
Input
1
C6
22
SDQ60
Input
1
B5
23
SDQ28
Input
1
C7
24
SDQ26
Input
1
B7
25
SDQ58
Input
1
E8
26
SDQ24
Input
1
C8
27
RSVD
Input
1
C9
28
SDQ23
Input
1
D8
29
SDQ57
Input
1
E10
30
SDQ53
Input
1
B9
31
SDQ5
Input
1
E11
32
SDQ20
Input
1
E9
33
SDQ56
Input
1
AH27
34
SBA1
Output
N/A
®
Intel 82845 MCH for SDR Datasheet
Testability
R
Table 25. XOR Chain 2
®
Chain 2 Ball
Element #
Signal Name
Note
Initial Logic Level
D10
1
SDQ54
Input
1
C10
2
SDQ21
Input
1
C11
3
SDQ52
Input
1
F9
4
SDQ22
Input
1
B11
5
SDQ19
Input
1
B13
6
SDQ16
Input
1
G11
7
SCKE4
Input
1
C12
8
SDQ18
Input
1
F11
9
SDQ51
Input
1
C13
10
SDQ49
Input
1
D12
11
RSVD
Input
1
E12
12
SDQ50
Input
1
E13
13
SDQ17
Input
1
G14
14
SCK5
Input
1
G13
15
SCK1
Input
1
F15
16
SCK9
Input
1
E15
17
SMA11
Input
1
G16
18
SCK8
Input
1
E16
19
SDQ65
Input
1
E18
20
SDQ47
Input
1
F17
21
SBS0
Input
1
F19
22
SMA7
Input
1
G18
23
SMA9
Input
1
G20
24
SMA5
Input
1
G19
25
SMA8
Input
1
F21
26
SMA2
Input
1
G21
27
SMA3
Input
1
E22
28
SDQ43
Input
1
G24
29
SCS5#
Input
1
G23
30
SRAS#
Input
1
G25
31
SCS8#
Input
1
H23
32
SCS0#
Input
1
J25
33
SCAS#
Input
1
AG28
34
SBA2
Output
N/A
Intel 82845 MCH for SDR Datasheet
141
Testability
R
Table 26. XOR Chain 3
142
Chain 3 Ball
Element #
Signal Name
Note
Initial Logic Level
G10
1
SCKE0
Input
1
G12
2
SMA12
Input
1
G15
3
SCK4
Input
1
F13
4
SCK0
Input
1
C14
5
SCB3
Input
1
E14
6
SDQ48
Input
1
D14
7
SCB7
Input
1
C15
8
SCB6
Input
1
G17
9
SBCS1
Input
1
C16
10
SDQ64
Input
1
D16
11
SCB5
Input
1
B15
12
SCB5
Input
1
C17
13
SDQ15
Input
1
B17
14
SCB4
Input
1
D18
15
SDQ46
Input
1
E17
16
SMA10
Input
1
B19
17
RSVD
Input
1
C18
18
SDQ14
Input
1
E19
19
SMA6
Input
1
C19
20
SDQ13
Input
1
C20
21
SDQ45
Input
1
D20
22
SDQ12
Input
1
C21
23
SDQ11
Input
1
E20
24
SMA4
Input
1
B21
25
SDQ44
Input
1
E21
26
SMA1
Input
1
C22
27
SDQ10
Input
1
D22
28
SDQ42
Input
1
C24
29
SDQ40
Input
1
C23
30
RSVD
Input
1
B23
31
SDQ9
Input
1
D24
32
SDQ7
Input
1
G22
33
SMA0
Input
1
E23
34
SDQ41
Input
1
®
Intel 82845 MCH for SDR Datasheet
Testability
R
Chain 3 Ball
Element #
Signal Name
Note
Initial Logic Level
B25
35
SDQ6
Input
1
C25
36
SDQ38
Input
1
C27
37
SDQ3
Input
1
D27
38
SDQ35
Input
1
B27
39
SDQ36
Input
1
C26
40
RSVD
Input
1
F23
41
SDQ8
Input
1
E24
42
SDQ39
Input
1
E25
43
SDQ5
Input
1
E27
44
SDQ1
Input
1
N24
45
HI_STB#
Input
1
R24
46
AD_STB
Input
1
AG27
47
SBA3
Output
N/A
Chain 4 Ball
Element #
Signal Name
Note
Initial Logic Level
D26
1
SDQ4
Input
1
F25
2
SDQ37
Input
1
B28
3
SDQ2
Input
1
C28
4
SDQ3
Input
1
E28
5
SDQ33
Input
1
J24
6
SCS4#
Input
1
F26
7
RSVD
Input
1
H25
8
SCS9#
Input
1
K25
9
RSVD
Input
1
J23
10
SCS1#
Input
1
F27
11
SDQ0
Input
1
K23
12
RSVD
Input
1
G28
13
SDQ32
Input
1
G27
14
SWE#
Input
1
M27
15
HI_8
Input
1
M24
16
HI_10
Input
1
N28
17
HI_9
Input
1
L28
18
HI_6
Input
1
M25
19
HI_5
Input
1
Table 27. XOR Chain 4
®
Intel 82845 MCH for SDR Datasheet
143
Testability
R
Chain 4 Ball
Element #
Signal Name
Note
Initial Logic Level
N27
20
HI_2
Input
1
M26
21
HI_4
Input
1
N25
22
HI_STB
Input
1
L27
23
HI_7
Input
1
P25
24
HI_0
Input
1
P23
25
HI_3
Input
1
P24
26
HI_1
Input
1
R27
27
G_ADO
Input
1
R28
28
G_AD1
Input
1
U27
29
G_AD6
Input
1
R25
30
G_AD3
Input
1
T27
31
G_AD5
Input
1
T36
32
G_AD4
Input
1
U28
33
G_AD7
Input
1
R24
34
AD_STB0
Input
1
V27
35
G_AD9
Input
1
T25
36
G_AD2
Input
1
U27
37
G_AD8
Input
1
T24
38
G_AD12
Input
1
U24
39
G_AD13
Input
1
U25
40
G_AD14
Input
1
T23
41
G_AD10
Input
1
V24
42
G_AD15
Input
1
U23
43
G_AD11
Input
1
AE28
44
SBA4
Output
N/A
Chain 5 Ball
Element #
Signal Name
Note
Initial Logic Level
V25
1
G_C/BE0#
Input
1
W28
2
G_DEVSEL#
Input
1
W25
3
G_PAR
Input
1
Y25
4
G_C/BE2#
Input
1
W27
5
G_IRDY#
Input
1
V23
6
G_C/BE1#
Input
1
Y24
7
G_FRAME#
Input
1
Table 28. XOR Chain 5
144
®
Intel 82845 MCH for SDR Datasheet
Testability
R
®
Chain 5 Ball
Element #
Signal Name
Note
Initial Logic Level
W24
8
G_TRDY#
Input
1
AE23
9
WBF#
Input
1
W23
10
G_STOP#
Input
1
AA23
11
G_C/BE3#
Input
1
AA28
12
G_AD18
Input
1
Y26
13
G_AD17
Input
1
Y27
14
G_AD16
Input
1
AB27
15
G_AD20
Input
1
AB26
16
G_AD22
Input
1
AA25
17
G_AD26
Input
1
AA24
18
G_AD25
Input
1
AA27
19
G_AD21
Input
1
AC27
20
AD_STB1
Input
1
Y23
21
G_AD23
Input
1
AC25
22
G_AD28
Input
1
AB25
23
G_AD19
Input
1
AB23
24
G_AD24
Input
1
AB24
25
G_AD31
Input
1
AC24
26
G_AD29
Input
1
AC22
27
G_AD30
Input
1
AB24
28
G_AD27
Input
1
AE22
29
RBF#
Input
1
AF24
30
ST1
Input
1
AF22
31
PIPE#
Input
1
AF27
32
SB_STB
Input
1
AH25
33
G_GNT#
Input
1
AG25
34
ST0
Input
1
AG24
35
G_REQ#
Input
1
AG26
36
ST2
Input
1
AH17
37
HD61#
Input
1
AG16
38
HD55#
Input
1
AG17
39
HD56#
Input
1
AC16
40
HDSTBP3#
Input
1
AE11
41
HDSTBP2#
Input
1
AE27
42
SBA5
Output
N/A
Intel 82845 MCH for SDR Datasheet
145
Testability
R
Table 29. XOR Chain 6
146
Chain 6 Ball
Element #
Signal Name
Note
Initial Logic Level
AC27
1
AD_STB1
Input
1
AF27
2
SB_STB
Input
1
AE17
3
CPURST#
Input
1
AD17
4
HD62#
Input
1
AE16
5
HD63#
Input
1
AH15
6
HD57#
Input
1
AG15
7
HD54#
Input
1
AF16
8
HD59#
Input
1
AC16
9
HDSTBP3#
Input
1
AE15
10
HD60#
Input
1
AG14
11
HD52#
Input
1
AC17
12
HD58#
Input
1
AF14
13
HD51#
Input
1
AE14
14
HD53#
Input
1
AH13
15
HD49#
Input
1
AD15
16
DBI3#
Input
1
AG13
17
HD48#
Input
1
AC14
18
HD50#
Input
1
AF12
19
HD47#
Input
1
AG12
20
HD45#
Input
1
AE12
21
HD40#
Input
1
AE13
22
HD46#
Input
1
AH9
23
DBI2#
Input
1
AG10
24
HD43#
Input
1
AH11
25
HD44#
Input
1
AG9
26
HD38#
Input
1
AG11
27
HD42#
Input
1
AE11
28
HDSTBN2#
Input
1
AF10
29
HD41#
Input
1
AE10
30
HD36#
Input
1
AC12
31
HD33#
Input
1
AC11
32
HD32#
Input
1
AC10
33
HD39#
Input
1
AE9
34
HD34#
Input
1
®
Intel 82845 MCH for SDR Datasheet
Testability
R
Chain 6 Ball
Element #
Signal Name
Note
Initial Logic Level
AC9
35
HD35#
Input
1
AD9
36
HD37#
Input
1
AH7
37
HD24#
Input
1
AH5
38
HD31#
Input
1
AG8
39
HD27#
Input
1
Y4
40
DEFER#
Input
1
W7
41
RS1#
Input
1
AE24
42
SBA6
Output
N/A
Chain 7 Ball
Element #
SDR Ball name
Note
Initial Logic Level
AG6
1
HD29#
Input
1
AG5
2
HD16#
Input
1
AG7
3
HD28#
Input
1
AF6
4
HD19#
Input
1
AF8
5
HD30#
Input
1
AE6
6
HDSTBN1#
Input
1
AG4
7
DBI1#
Input
1
AH3
8
HD25#
Input
1
AE8
9
HD18#
Input
1
AG2
10
HD17#
Input
1
AF4
11
HD26#
Input
1
AH2
12
HD20#
Input
1
AE5
13
HD23#
Input
1
AG3
14
HD22#
Input
1
AF3
15
HD21#
Input
1
AD7
16
HD10#
Input
1
AC7
17
HD11#
Input
1
AC8
18
HD14#
Input
1
AD5
19
DBI0#
Input
1
AC6
20
HD12#
Input
1
AE2
21
HD15#
Input
1
AB7
22
HD9#
Input
1
AE3
23
HD8#
Input
1
AD4
24
HDSTBN0#
Input
1
Table 30. XOR Chain 7
®
Intel 82845 MCH for SDR Datasheet
147
Testability
R
148
Chain 7 Ball
Element #
SDR Ball name
Note
Initial Logic Level
AC3
25
HD13#
Input
1
AB5
26
HD1#
Input
1
AC5
27
HD5#
Input
1
AA6
28
HD7#
Input
1
AA5
29
HD2#
Input
1
AB3
30
HD3#
Input
1
AA3
31
HD6#
Input
1
AB4
32
HD4#
Input
1
AA2
33
HD0#
Input
1
Y5
34
HIT#
Input
1
Y7
35
BPRI#
Input
1
W6
36
RS2#
Input
1
Y3
37
HITM#
Input
1
U7
38
HTRDY#
Input
1
W5
39
HLOCK#
Input
1
V7
40
BR0#
Input
1
W3
41
BNR#
Input
1
W2
41
RS0#
Input
1
V5
43
DBSY#
Input
1
V4
44
DRDY#
Input
1
AE25
45
SBA7
Output
N/A
®
Intel 82845 MCH for SDR Datasheet
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