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SubjectRe: IDE-DMA strangeness (another one)
On 1 Dec 1998, Mark Gray wrote:

> Rik van Riel <H.H.vanRiel@phys.uu.nl> writes:
>
> >
> > Hi,
> >
> > I've just moved my IDE disks around, taking out an old
> > disk and moving my new 6.4GB disk from hdd to hda.

This sounds normal.............name your chipset........did you happen to
run 'W-word'? Older PIIX's lie about capabilty because of crappy BIOS
writers/hackers............

> > With this move I saw in improvement (hdparm -t) from 3
> > to 8.4 (!) MB/second... Now I wonder what kind of bug

Your PIO3/4 disk that had a recomended of 180ns for DMA was locked out.
The previous location was a non-correctly allocated PDT.
Skip the assigned PIO settings in the bios and use AUTO/AUTO

> > in the Linux I/O subsystem could hold performance back
> > _that_ badly.

Not a bug...........8.4 MB/second is a UDMA drive at DMA mode 2
on an 430HX/VX/TX, and I bet the usable buffer is more.
Note that the new kernel code auto set multi-write to max.

> > Of course both benchmarks were done on a completely
> > unloaded IDE chip/PCI bus...
>
> Some motherboards use a crippled controller for ide1 in the belief
> that it will only be used for cdroms.

That is usually because of lazy BIOS writers/hackers (ass)(u)(me)
"Nobody will use more than two hardrives"

> > cheers,
> >
> > Rik -- now completely used to dvorak kbd layout...
>
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>

Cheers,
Andre Hedrick
The IDE-FNG for Linux
The APC UPS Specialist for Linux

http://www.dyer.vanderbilt.edu/server/udma/
http://www.dyer.vanderbilt.edu/server/apcupsd/apcupsd-3.5.0.bin.tar.gz






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