Technical Note
Why Turbo 1394?
Q: What is Turbo 1394?
A: Turbo 1394™ is Photometrics’ unique implementation
of data transfer through a standard FireWire® (IEEE 1394)
computer connection.
Q: Why did Photometrics® decide to use an implementation
of FireWire over our previous low-voltage differential
signaling (LVDS) connectivity?
A: The LVDS connectivity lacked the bandwidth required for
newer cameras. The theoretical maximum on our
implementation of LVDS at 16 bits is 16.5 MHz. In testing,
however, we found that actual speeds of 12-13 MHz required
the use of very short cables. Also, the LVDS PCI cards would
not function in PCIe-based computers or with other future bus
architectures. By designing Turbo 1394, we were able to
overcome these issues.
Q: What makes Turbo 1394 different from regular FireWire?
A: There are two main differences, each of which offers
distinct advantages for users. These differences are listed
(1) Turbo 1394 allows higher data throughput than standard
FireWire in an equivalent timeframe.
Q: How do we achieve higher throughput?
A: We have found a way to increase the bandwidth beyond
the published specifications. By pushing the capacity of
FireWire, we’re able to achieve bandwidth that supports the
same (or better) data rates than our LVDS cameras are able to
provide — even at 16 bits per pixel. With our special
implementation of FireWire, we can guarantee that all frames
are delivered. We do not have to drop frames or insert dark
frames (as other camera manufacturers do).
Q: How does Turbo 1394 eliminate these extra clock cycles?
A: Turbo 1394 allows the camera direct memory access
(DMA) into the application’s frame buffer rather than into a
driver buffer (unlike other camera manufacturers). Our
streamlined approach avoids forcing the user to double buffer
the data, which saves the host computer clock cycles and
affords it a greater ability to perform other tasks, such as
processing (see Figure 1).
Photometrics continually strives to optimize the electronic
design of our cameras in order to further enhance their
performance capabilities. Turbo 1394 is another example of
this ongoing effort.
FireWire is a trademark of Apple Computer, Inc., registered in the U.S. and other countries.
Standard Implementation
Photometrics Implementation
Figure 1.
(2) Turbo 1394 saves your computer from having to perform
the extra clock cycles that would need to be done under a
standard FireWire implementation, thus allowing the
computer to perform faster.
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