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Date:      Wed, 29 Mar 2000 19:44:57 +0200 (CEST)
From:      Soren Schmidt <sos@freebsd.dk>
To:        dillon@apollo.backplane.com (Matthew Dillon)
Cc:        adsharma@sharmas.dhs.org (Arun Sharma), freebsd-smp@FreeBSD.ORG
Subject:   Re: SMP and vn
Message-ID:  <200003291744.TAA47172@freebsd.dk>
In-Reply-To: <200003291706.JAA63514@apollo.backplane.com> from Matthew Dillon at "Mar 29, 2000 09:06:30 am"

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It seems Matthew Dillon wrote:
> 
>     I think there are two possibilities:
> 
>     First, since the disk light is left on there is a good chance that the
>     problem is in the UDMA66 code, try compiling the kernel up with that
>     disabled (i.e. if you have the ATA_ENABLE_ATAPI_DMA kernel config
>     option set, comment it out and recompile).

ATA_ENABLE_ATAPI_DMA only controls _ATAPI DMA_ not ATA DMA, ie it
only control DMA usage on ATAPI devices like CDROM, tape etc.
This is because there is alot of ATAPI devices out there that claim
that they support DMA, but actually doesn't work so ATAPI DMA will
not be tried in a kernel without the ATA_ENABLE_ATAPI_DMA option.

If you want to disable DMA entirely you have to use the sysctl hw.atamodes,
for more info "man ata". 
 
-Søren


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