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SubjectRe: Incorrect UDMA timing on VIA vt82c596b
On Fri, Oct 06, 2000 at 12:07:27PM -0500, Jordan wrote:

> I have been using the 2.4..0 test series for quite some time now on a
> machine with Redhat 6.2 and gcc 2.95.2 running on a Pentium III 733
> Flip-Chip on a Tyan Trinity 400 (S1854) Motherboard. Until the recent
> kernels my IBM 75 GB 7200 RPM Deskstar would only use PIO transfer modes
> and only my Kenwood CDROM would correctly turn on its DMA and come up as
> UDMA(33). With test8 and the test9 series I have been able to get all
> of my drives (IBM, Kenwood, Zip and Plextor CDRW) to turn on DMA and the
> IBM and Kenwood will come up as UDMA(33). The only problem is that I
> have as of test9 tried the stock ide drivers and ide-timing file for my
> VIA vt82c596b controller and I can't get the IBM to come up as UDMA(66)
> as it should. This shouldn't be a problem in my mind as the drive is
> ATA-100 compatible and the controller correctly gets recognized as a
> UDMA(66) controller.

Try the "ignore byte93" option in the IDE menu. The IBM doesn't try to
do UDMA66 because the ZIP drive kills its 80-wire cable detection
mechanism. If you ignore byte93, which is where the IBM drive tells the
system what it thinks about the cable, the system will enable UDMA66.

> The other puzzling factor is that my friend has a
> smillar VIA chipset on an Athlon board by Procomp and when I built his
> 2.4.0-test9 with the stock ide drivers his 40 GB Maxtor comes up as
> UDMA(66) and his 15 GB Maxtor comes up as UDMA(33) which are the correct
> values. I have my IBM as master on the primary channel, my Zip as slave
> on the primary channel, my Kenwood and Master on the secondary channel,
> and my Plextor as slave on the secondary channel. Is this a problem
> with the code for my controller or do I need to re-order my drives on
> the IDE cables. Thanks for any help.

For fastest operation I'd suggest moving the Kenwood to hdb and the ZIP
to hdd. That way you won't need to ignore the byte93 setting. (Assuming
you really DO have the special UDMA66 80-wire cable).

--
Vojtech Pavlik
SuSE Labs
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