Linux-kernel mailing list archive 1997-47,: Re: Triton DMA

# Re: Triton DMA

mlord (mlord@pobox.com)
Fri, 28 Nov 1997 18:40:58 -0500

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Shaw Carruthers wrote:
>
> > > a) Some BIOSes turn DMA on when they shouldnt
> >
> > Rare, and Linux makes its own decision anyway.
>
> My TX97-E bios starts up my QUANTUM FIREBALL ST2.1A as UDMA 2, but linux
> 2.1.66 sets DMA off. I have to turn it on with hdparm. I am not clear why
> linux does this. How does linux make its decision?

Linux currently does not include full support for UDMA
(need to add CRC checking and error handling to do a proper job),
so it does not use DMA by default in your case.

You can still turn it on (hdparm -d1), and it will mostly work
but without full error detection/correction.

> OTOH linux and the bios both start my ST51270A on pio 4, which seems
> clearly correct as turning on DMA gives occasional timing errors.

Linux does NOT set PIO modes on drives (unless you use hdparm to do it),
so I am not sure what you meant by that.

    --
    mlord@pobox.com
    The Linux IDE guy

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