Re: [PARPORT] ECP mode transfers in 2.4.x kernels

From: Philip Blundell (
Date: Mon Sep 10 2001 - 14:37:51 EDT

  • Next message: Philip Blundell: "Re: [PARPORT] ECP mode transfers in 2.4.x kernels"

    >That's something I hadn't thought of trying. I've done so (by setting
    >dma=none in /etc/modules.conf) and it works with no errors. The
    >interesting thing is that it's *faster* without DMA than with DMA --
    >on one printer I get 980 kBytes/sec without DMA vs 490 kBytes/sec with
    >DMA (in ECP mode); on the other printer I get 540 kBytes/sec without
    >DMA vs. 340 kBytes/sec with DMA. In compatibility mode it is also
    >faster without DMA but not as dramatically so.

    Heh. Well, that's good news. Actually it doesn't surprise me all that much
    that PIO is faster. It takes time to set up the registers in the DMA
    controller and tell it to go, and to service the interrupt that tells you it's
    finished, and it probably can't move data across the bus any faster than the
    CPU can anyway. The real advantage of DMA is that it frees the processor to
    go and do something else, so you should (at least in theory) get better
    performance from other tasks during printing.

    >I think at least for now I think I'm just going to turn DMA off.

    Seems like a good plan.


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