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SubjectRe: 2.2.9 probs (ide hd, quota, 128MB (+sort))
On Mon, 24 May 1999, Guest section DW wrote:

>
> > The ide-dma code does/can not enable UDMA-3/4; therefore, it is not used.
>
> Maybe I should not ask since I do not know about these things,
> but you said that this was a ATA/66 problem. How precisely is

I do not know yet, but I will ramble about what I have observed and tested.

> this caused? And what is the problem, if disabling DMA does not cure it?

There appears to be an ugly transistion period in the standard.

There are chipsets that claim to ATA-66 compliant....
Translation ::

We can detect/trigger but not make use of UDMA-3/4.
Known offenders are the ALI1543 AGP-PRO and VIA???? AGP-PRO.
This is different from the ALI1543 TX-PRO and VIA82c568 TX-PRO.
It appears through imperical tests that the evolution of the TX-PRO to the
AGP-PRO as gone very wrong. This may not have any thing to do with
Intel's BX chipset, but something is very bad. There appears to be no bit
sensing of capablity in all directions.

I am now in agreement with Mark's suggestion to leave this alone for a
while. The problem is that I need to still figure out how to speed break
drive chipset combinations. Many componets are over-promising and
under-delivering. The short is that BIOSes need to be able to throttle
back the drives if they can not perform the IO, but they don't.

Maybe if this guy disables UDMA and forces DMA mode 2 in the BIOS, we may
be able to get a correct drive table report. A crippled drive is better
than one that is unusable.


There are drives that claim to ATA-66 compliant....
Translation ::

We can fake the detection with our interface, but we can not do it.
Reported offender is the Fujitsu MPDxxxx drives, but this was only in
combination with the AGP-PRO boards. I tested this on the Ultra66 and it
correctly reported ATA-33 and no goofballing/fudging.

As for my answers that are confusing, so is the standard.

Everyone is over selling what they can do, and under delivering.

ATA-66 is only verified successful on the Promise Ultra66 chipset.
There a only a few drives that can correctly report, handle, and perform
ATA-66.

WDC AC29100D FwRev=J74OA30K real good fastest yet at ~17MB/sec
WDC AC310200R FwRev=17.01J17 a brick at ~13MB/sec
IBM-DJNA-371800 FwRev=J78OA30K speed untested

Note that WDAC3xxxxxR and/or firmware 17.01J17 is a kludge drive that
technically works, but is slower than many ATA-33 drives.

Andre Hedrick
The Linux IDE guy



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