From: Richard Stover (
Date: Tue May 09 2000 - 20:20:05 EDT

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    Hi Derek,

    I have tried the parallel port on my motherboard (from ASUS) and a
    ISA parallel port card. Both give about 1 byte per 2 microseconds
    (500 Kbyte/sec) transfer rate using DMA in ECP mode. This is much slower
    the top ECP rate of about 1 byte per 0.5 microseconds. I assume the
    actual rate is limited by the ISA bus, but I'm not sure.

    For the highest rates that our camera will produce I need 1 megabyte/sec
    continuous transfer, so we are now looking at a PCI bus solution. We
    tried a SIIG
    Cyberparallel I/O PCI card but it seems it doesn't even support DMA
    or interrupts. The company was also completely non-responsive to
    my inquiries.

    We are now designing our own PCI interface. If money is no object you
    might check out the products from a company called EDT.

    I don't know that much about ppdev or the standard linux driver.
    I wrote my own to provide double-buffered input for continuous
    high throughput, some specialized handshaking for our camera, and the
    ability for a user-level program to process the data as it is
    coming in via DMA.

    You might be able to tell if the driver has allocated a DMA channel
    by looking at /proc/dma.


    Richard Stover                       email:
    Detector Development Laboratory
    UCO/Lick Observatory                 Voice: 831-459-2139
    Natural Sciences Bldg. 2, Room 160
    University of California             FAX:   831-459-2298
    Santa Cruz, CA 95064  USA            FAX:   831-426-5244 (Alternate)

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