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2001 Dec 30 17:02

The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

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Re: [vox-tech] Ultra DMA support
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Re: [vox-tech] Ultra DMA support



DMA is a seperate issue.

To boot off the external array theres a couple ways to
do it, all tricky.

One is to rewrite /etc/fstab to use /dev/hde or whatever
comes up as the first external ide bus.

Another is to enable the kernel option IDE=reverse or similar,
it's documented under the kernel make config, the description
is something like boot external ide busses first or similar, and
requires a LILO/kernel boot options similar to IDE=reverse.

Once enabled the external IDE bus will be /dev/hda and allow
for a disk that was installed on the primary IDE bus to
be used on the external bus.

BTW I wouldnt' expect dramatically better performance on the
HPT/UDMA66 vs the old udma33.  Unless you think it's fun, want
to explore etc I wouldn't bother.  Most desktop use won't notice
it the bottleneck is usually the head rate/seek speed not the
speed of the IDE bus.    Not to mention most desktop use isn't
particularly disk limited.

Turning on DMA via hdparm -d 1 /dev/hda or similar often will
make a dramtic improvement to performance assuming your hardware
works as it should.  

On Tue, Mar 13, 2001 at 11:12:01AM -0800, Jan Wynholds wrote:
> 
> --- Joshua Poppe <jjpoppe@ucdavis.edu> wrote:
> > My motherboard (Abit BE6) supports Ultra DMA 33 and
> > 66 but it is only available on ide2 and ide3 (3rd
> > and 4th eide slots).  I found the chip (highpoint
> > tech.) in the hardware compatibility list on
> > RedHat.com (I am running 7.0) and it is supported,
> > but harder to install if it is not the primary ide
> > (ide0, ide1). I tried telling the kernel that I have
> > my HD connected to UDMA, but alas the kernel didn't
> > feel like listening.  I have a clean install of
> > Linux on this drive without using UDMA and now I
> > would like to use my previous install with the UDMA.
> >  I am pretty new to Linux (meaning I know little
> > about it but I can navigate a Unix system pretty
> > well).  Any help or advice would be much
> > appreciated.  Also, I would be wiling to reinstall
> > if needed.  
> > 
> > Thanks,
> > Josh
> > 
> Hey Josh:
> 
> I don't think you need to reinstall.  I think that
> maybe you don't have ide dma compiled for your kernel.
>  RedHat does some funny stuff with the kernel that
> they ship.  At least, when I installed 7.0, ide dma
> wasn't compiled with the 2.2.16-22 kernel that came
> with it.
> 
> How are you 'telling' the kernel to use dma?  hdparm? 
> hdparm only works with the support from the kernel
> that it needs for the higher speeds.
> 
> If you need help recompiling kernel, just ask :).
> 
> Jan
> 
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