[Soekris] 4801 CF, NetBSD-current

[David Young]

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
> diffferent.

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?

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933