[Soekris] 4801 CF, NetBSD-current
dyoung at pobox.com
Wed Oct 20 11:14:05 UTC 2004
On Wed, Oct 20, 2004 at 12:44:43PM +0200, Bernd Walter wrote:
> On Wed, Oct 20, 2004 at 09:34:18AM +0100, Chris Boot wrote:
> > It sounds a lot to me like problems with DMA, rather than the card
> > itself. Try disabling DMA on the CF card at boot time. There was a post
> > about this a few weeks back about this, and your CF card even rings a
> > bell (the other was a SanDisk as well). AFAIK CF cards usually work via
> > PIO anyway.
> The story behind DMA is that originally CF cards didn't support DMA
> and the specification had no wiring defined for DMA.
> Now there is a DMA specification and modern cards tend to support it
> as well.
> Now we end up with an IDE controller and a media that are both DMA
> capable, but without DMA wiring and an OS that doesn't know about
> the bad wiring.
> Modern SanDisk medias support DMA and you can buy them with DMA
> feature reporting enabled or disabled - IIRC you get get a tool from
> them to switch as well - that is why same looking media behave
I'm a little confused. Do modern SanDisk media actually support DMA, or
do they claim to support DMA, but nevertheless fail because of bad wiring?
David Young OJC Technologies
dyoung at ojctech.com Urbana, IL * (217) 278-3933
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