Mini-ITX Addendum Version 2.0 to the microATX Motherboard

Mini-ITX Addendum Version 2.0
To the microATX Motherboard
Interface Specification Version 1.2
October 2010
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Contents
Revision History..................................................................................................................... 4
1
Executive Summary ........................................................................................... 5
1.1
1.2
1.3
1.4
2
6
6
6
6
Layout .............................................................................................................. 8
2.1
2.2
2.3
2.4
3
Terminology ...........................................................................................
Reference Documents ..............................................................................
Benefits to Users ....................................................................................
Benefits to Manufacturers ........................................................................
Board Dimensions ................................................................................... 9
Mounting Hole Placement ......................................................................... 9
Connector Placement.............................................................................. 11
2.3.1
Thin Mini-ITX Back Panel I/O...................................................... 11
Height Constraints ................................................................................. 11
2.4.1
Mini-ITX: Primary (Component) Side Height Constraints ................ 11
2.4.2
Thin Mini-ITX: Primary (Component) Side Height Constraints ......... 12
2.4.3
Secondary (Bottom/Solder) Side Height Constraints ..................... 14
2.4.4
Thin Mini-ITX System Considerations .......................................... 14
Power Supply Information .................................................................................. 16
Figures
Figure
Figure
Figure
Figure
Figure
Figure
1.
2.
3.
4.
5.
6.
Example Mini-ITX Layout for SFF Desktop .............................................. 8
ATX, microATX, and Mini-ITX Mounting Holes.......................................... 9
Mini-ITX Board Diagram ...................................................................... 10
Thin Mini-ITX Back Panel I/O ............................................................... 11
Mini-ITX Maximum Component Height Restrictions ................................. 12
Thin Mini-ITX Maximum Component Height Restrictions .......................... 14
Tables
Table 1. Mini-ITX Addendum Feature Summary .................................................... 5
Table 2. Compares ATX, microATX, and Mini-ITX Board Dimensions ........................ 9
Table 3. Motherboard Mounting Hole Locations .................................................... 10
3
Revision History
Revision
Number
Description
Revision Date
2.0
Added Thin Mini-ITX definition.
Oct, 2010
1.1
Minor corrections made. Title changed to:
Feb, 2009
‘Mini-ITX Addendum Version 1.1 To the microATX
Motherboard Interface Specification Version 1.2’
to reflect full name of mATX document name.
1.0
Initial release.
Feb, 2009
§
4
1
Executive Summary
The Mini-ITX addendum to the microATX Motherboard Interface Specification details
the use the Mini-ITX form factor standard, developed by Via Technologies Inc, for
compatibility with Intel based platforms. This document defines only the specific
features in Intel’s Mini-ITX based platforms that differ from those of microATX and
should be used in conjunction with the governing microATX specification.
A smaller motherboard layout offers system developers the ability to create new and
innovative system designs. This smaller version of microATX allows and encourages
developers to build within the sub 8 liter chassis volume for a variety of new
applications.
Described within this document are requirements and characteristics of a Mini-ITX
motherboard, so that a motherboard may function and fit appropriately when paired
with a Mini-ITX chassis. Beyond this, it does not detail processor, memory, graphics
or other system features required to meet the Mini-ITX form factor. These items are
left to system designers and integrators within the guidelines of the microATX
specification.
A further refinement of Mini-ITX boards is the Thin Mini-ITX board definition. Its
smaller size enables system integrators to integrate sub-4 liter systems, such as Tiny
PCs and All-In-One PCs, using a standard building block approach.
Table 1. Mini-ITX Addendum Feature Summary
Feature
Benefit
170mm x 170mm motherboard size
Smaller board size enables a smaller system
size.
Mini-ITX: Standard microATX 1.2 or later I/O
panel
ATX I/O shield does not need to be retooled.
Motherboard can be used in an ATX, microATX,
or Mini-ITX chassis.
Thin Mini-ITX: A Mini-ITX board targeted for
smaller system form factors with a 20mm tall
PCB and component volumetric, and a 1” back
panel I/O height
A Thin Mini-ITX board can use a thin back
panel I/O shield when targeted for Tiny PCs
and AIOs. The same board can be used in a
Mini-ITX, microATX, and ATX chassis when
used with a regular ATX I/O shield.
Same motherboard mounting holes as in
microATX
Compatible with microATX chassis. No need to
retool current chassis.
Current processor and future processor
technologies
Chassis will work for multi generation socketed
processor technology.
This addendum does NOT define:

Specific power supply form factors

Thermal design guidance to chassis vendors (covered in TASC guide listed in
Reference Documents)
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The Mini-ITX Addendum To the microATX Motherboard Interface Specification is a
public document intended for widespread application in many types of systems. It is
available through a public website located at:
http://www.formfactors.org
1.1
Terminology
Term
1.2
Description
Small Form Factor (SFF)
8-19 liter chassis (IDC* definition)
Ultra SFF (uSFF)
4-8 liter chassis (IDC* definition)
Tiny PC
Less than 4 liter chassis (IDC* definition)
All-In-One (AIO) PC
An All-In-One is a desktop PC with a display built into the main
computing unit (IDC* definition)
Reference Documents
The following reference documents are posted on the public web site at:
http://www.formfactors.org
Document
microATX Motherboard Interface Specification Version 1.2
SFX 12V Power Supply Design Guide
TFX 12V Power Supply Design Guide
Thermally Advantaged Small Chassis or TASC [pronounced ‘task’] (Thermal Design Guide)
1.3
Benefits to Users
Trends in the industry indicate that users require a smaller and lower cost solution for
their PC needs. Mini-ITX’s smaller board size and lower height keep-out zones enable
a reduced sized chassis as it sits on the user’s desk, is mounted on a display, or
comes in any other innovative form factor. These changes also enable a PC to be
designed into various aesthetic shapes and sizes. The Thin Mini-ITX board variation
leverages Mini-ITX’s advantages, while enabling even thinner systems.
1.4
Benefits to Manufacturers
By manufacturing to the standard or thin variations of the Mini-ITX specification,
motherboard manufacturers and chassis manufacturers can guarantee a better
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compatibility between their products. They can also capitalize on the benefits of a
reduction in total system costs because of a reduced system size. This specification
allows chassis vendors to design their product targeting the soldered down, low power
processors all the way up to high performance, multi-core processors. It eliminates
the need for them to design targeted chassis for each platform.
§
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2
Layout
This section describes the mechanical specifications of the Mini-ITX and Thin Mini-ITX
form-factor motherboards. Size, mounting hole placement, connector placement, and
component height constraints are specified. System components such as hard drives,
disk drives, and power supplies are not specified; however, it is generally
recommended to consider what would facilitate assembly, as well as not place
components such that they block fan inlets. An example layout is depicted in Figure
1.
Thin Mini-ITX is a variant of standard Mini-ITX and shares most of the same
requirements. Requirements are only different where new specifications are
specifically defined for Thin Mini-ITX.
Figure 1. Example Mini-ITX Layout for SFF Desktop
NOTE:
8
Depicted system is approximately 8L with standard desktop components.
2.1
Board Dimensions
Table 2. Compares ATX, microATX, and Mini-ITX Board Dimensions
2.2
Dimension
ATX
microATX
Mini-ITX
Maximum width Allowable
305mm
244mm
170mm
Maximum depth Allowable
244mm
244mm
170mm
Mounting Hole Placement
Mini-ITX utilizes a subset of ATX mounting holes. To avoid damage to traces on
motherboards, chassis standoffs in any locations not specified should be removable or
not implemented at all. See Figure 2 for relative hole locations compared to ATX and
microATX motherboards.
Figure 2. ATX, microATX, and Mini-ITX Mounting Holes
NOTE:
Board is shown oriented with the rear of the board towards the top.
NOTE:
The lighter portion indicates the approximate region of the Mini-ITX form factor.
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Table 3. Motherboard Mounting Hole Locations
Form Factor
Mounting Hole Locations
Mini-ITX
C,F,H,J
microATX
B,C,F,H,J,L,M,R,S
ATX
A,C,F,G,H,J,K,L,M
Figure 3. Mini-ITX Board Diagram
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2.3
Connector Placement
For Mini-ITX, all connector locations as well as allowable placement area for I/O
connectors on the back panel are described and can be found in the microATX
Interface Specification.
2.3.1
Thin Mini-ITX Back Panel I/O
The Thin Mini-ITX Back Panel I/O area is defined in Figure 4. The width of the back
panel I/O aperture and the location of the motherboard relative to the I/O aperture
are the same as Mini-ITX. This allows a Thin Mini-ITX board to be used in either a
Thin Mini-ITX chassis, or a Mini-ITX and larger compatible chassis when using an
appropriate I/O shield.
The thickness of the PCB and the topside I/O connectors shall fit within the .787”
(20mm) height shown in Figure 4. See section 2.4.2 for additional discussion.
Figure 4. Thin Mini-ITX Back Panel I/O
2.4
Height Constraints
2.4.1
Mini-ITX: Primary (Component) Side Height Constraints
One major advantages of the Mini-ITX form factor is its backward-compatibility with
the ATX specification. The Mini-ITX motherboard can be installed in any ATX chassis.
Figure 5 shows the required Mini-ITX maximum component height constraints for
the components on the PC board. For full compliance with Mini-ITX, and to prevent
interference with the chassis structure, power supply, or peripherals, the motherboard
components should not exceed the height limit in each zone defined. Similarly,
compliant power supplies, peripherals, and chassis features should not extend into the
motherboard component area.
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Figure 5. Mini-ITX Maximum Component Height Restrictions
Notes:
2.4.2

All dimensions in the above figure are in millimeters (mm).

The 57mm height restriction in Area A applies to the PC board component height.
The actual height of the chassis should include any dynamic excursion
considerations for shipping as well as needs to facilitate alternative cooling
solutions or airflow considerations.

For the Intel boxed processor fan heat sink, it is strongly recommended not to
place components between fan inlet and chassis side vent by leaving space
between chassis wall and area A open.

The component height requirement assumes a motherboard thickness of 1.57 mm
(.062”).
Thin Mini-ITX: Primary (Component) Side Height
Constraints
Figure 6 shows the required Thin Mini-ITX volumetric envelope for the PCB and all
motherboard components. For full compliance with Thin Mini-ITX, and to prevent
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interference with the chassis structure and other system components, the
motherboard components must not exceed the height limit in each zone defined.
In Area A, the thickness of the PCB and the topside components shall fit within the
.787” (20mm) height shown in Figure 6. With this in mind, motherboard designers
may exercise tradeoffs between board thickness and the height of I/O components as
necessary. For example, a .062” (1.57mm) PCB would allow .725” (18.43mm) for
topside components, while a .093” (2.36mm) PCB would allow .694” (17.64mm).
Chassis features and system components must not extend into the motherboard
component area. Additionally, space must be permitted around the motherboard by
the chassis and other system components to allow for dynamic excursion
considerations, as well as needs to facilitate alternative cooling solutions or airflow
considerations.
Depending on the needs of the system, components that interface with the
motherboard but are not part of it, such as a CPU heatsink, may fit within the
volumetric established in Figure 6 or extend outside of it. Any components that
extend through the motherboard volumetric must be selected in cooperation with the
chassis to ensure there are no interference issues. The motherboard may have its
own specific keep-in or keep-out requirements, such as around a CPU for its heatsink,
which may also need to be considered.
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Figure 6. Thin Mini-ITX Maximum Component Height Restrictions
2.4.3
Secondary (Bottom/Solder) Side Height Constraints
No height restraints on secondary side are added or removed from what is specified in
the microATX Motherboard Interface Specification.
2.4.4
Thin Mini-ITX System Considerations
While the low profile design of a Thin Mini-ITX motherboard creates the opportunity
for smaller PCs, system space must be allowed for factors such as airflow and cabling.
Board headers and the cable connectors they mate to should be selected with size and
orientation in mind. The use of tall headers which are perpendicular to the
motherboard and/or long cable connectors increase the chance of interference with
chassis components immediately over a Thin Mini-ITX board.
System integration challenges can be addressed in a variety of ways, including:
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
Carefully considering venting and fan/blower strategies to ensure proper cooling
can be achieved in a small chassis.

Minimizing the size of board headers and cable connectors.

Using board headers which are parallel or angled to the PCB, provided sufficient
space around and/or on the board is included in the system design for proper
cable mating and connector space.
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3
Power Supply Information
Provided the very different needs of the platforms that fit in the small desktop form
category, this specification does not attempt to define a standard for the power supply
to match with the Mini-ITX motherboard specification. Instead it recommends that
manufacturers consider using a:

SFX, TFX or FlexATX* are available power supply form factor for chassis greater
than 4 liters.

External power adapter for chassis less than 4 liters and All-in-One desktop
PCs.**
* Refer to the microATX Motherboard Interface Specification for information on power
supply requirements.
** Refer to related system design guides for information on AIO power supply
requirements.
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