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Message
From: Stephen Williams<steve@i...>
Date: Fri Feb 10 21:36:11 CET 2006
Subject: [pci] Anyone have a Specification for PCI Express?
Ludwig Jaffe wrote:
> I want to develop the kernel-accelerator-device <
> http://www.openhardware.de/digital/kad/ > which is a PCI-Card having
> reprogrammable FPGAs on it
> to accelerate the linux-kernel for tasks like AES, video transcoding.
> Additionally the KAD will be an universal development-
> plattform. So one can build an oscilloscope, Logic-Analyzer,
> pattern-generator, function-generator, software-definded Radio
> (Receiver, Transmitter), and even an incircuit emulator for some
> controllers. It depends only on cores which are to be written and
> Add-On-Modules that are to be designed. The KAD is as open as possible.
>
> The KAD will base on wishbone. So the PCI2WB-Bridge is essential. A
> PCI-Express2WB-Bridge would be great!
> Is your Design an addon for the PCI2WB-Bridge? If so, it would be great,
> Hagen (www.chipforge.org) and I would be pleased to support you.
I'm intrigued. I see it's potential value as a software accelerator
(i.e. a gimp accelerator, etc.) but I think there are some issues
that may bite you.
Worst is that the bus mastering capabilities of the pci_bridge32
WB-to-pci bridge are weak. I found while doing a video transmitter
that I could not get adequate speed for DMA out of host memory for
long bursts. Short bursts (128 words or so) are good, but when one
wants to read megabytes from the host, the burst fifos stall often
and anyhow do not support continuous pipelined bursts. So data
transfer is less then 1/2 what one would expect for PCI. So the
core PCI will need work.
ETc.
--
Steve Williams "The woods are lovely, dark and deep.
steve at icarus.com But I have promises to keep,
http://www.icarus.com and lines to code before I sleep,
http://www.picturel.com And lines to code before I sleep."
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