From: Peter Pregler (
Date: Sat Mar 25 2000 - 08:08:45 EST

  • Next message: Eric Morgan: "[PARPORT] Parallel Zip and SuSE 6.3 - Similar problem in RedHat 6.1"

    On 23-Mar-2000 Richard Stover wrote:
    > On my own project, we need to run at something close to
    > the rated 2 megabyte/sec capacity of ECP mode. But the
    > dma hardware seems to run at 2 microseconds/byte on the
    > system I'm using (4 times slower than our goal). Since this is
    > the first PC I've looked at in this detail I don't know if this is
    > going to be typical. Do you have any experience in this
    > area? Are there faster dma controller chips? Or is this set
    > by some old standards (like ISA)?

    I wrote a dma-handler for webcams based on the CPiA chip by VLSI. The
    maximum thruput I get right now is about 500kilobytes/sec with a 2.2.x
    kernel. I was told by the windows-driver writers, i.e. by the company that
    made the chips, that they got at least 800kilobytes/sec which is still way
    below the 2MB you refer to. I did not really try to tune the stuff. So I
    have no idea if the bottleneck is driver-software, hardware or the
    linux-kernel. Also I can use only 8bit DMA (i.e. I cannot assign a DMA>4
    to the parport). A 16bit DMA might boost performance for you. But I guess
    you need special parport-hardware for that. I have just a an standard
    Asus motherboards with onboard parport-controllers.



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