Re: 2.1.111: IDE DMA disabled?

Andrew Derrick Balsa (
Sun, 26 Jul 1998 22:33:56 +0200

Hi Alan,

On Sun, 26 Jul 1998, Alan Cox wrote:
>> a) Drive quality. Quantum drives are very reliable, but this is not
>> surprising since they worked with Intel to develop both DMA mode2 and
>> UDMA. IBM drives are good, too. Don't know about the others. I have seen
>> reports of entire batches of drives from Western Digital having
>> problems, and at least one Samsung drive I tested would consistently
>> malfunction under both DMA mode 2 and UDMA, even though it was specified
>> as UDMA compatible. The same equipment with an IBM drive has been
>> working flawlessly for a year, using UDMA.
>Ok lets approach this with more data.
>Andre - did you keep any of this data. Building a blacklist shouldnt be
>that hard. It may well be overencompassing but it has to be better than
>'dont do it'. Thats how you get the case where SCSI busses only run at 5Mhz.

:-) True. Just as an aside, UDMA is being pushed up to 66MB/s. The newest
chipset from VIA already does this, and Intel will probably release new
chipsets too. The first ATA-66 drives should appear early in 1999.

>Currently its
> Western Digital *
> Samsung [insert your drive here]

I will try to look for the exact reference. Right now I remember it was a
Samsung 2.5Gb supposedly UDMA compatible hard disk drive.

It's the only drive I ever had that failed consistently. Note that it also
failed under Windogs 95.

My white list is much longer, though:
1) Never had a problem with any Quantum drive, nor had any report of a problem
with them.
2) Never had any problems with IBM drives either. I have had almost every single
EIDE model they manufactured: 1.2Gb, 1.7Gb, 2.1Gb, 3.2Gb, 4.3Gb, 6.4Gb, 8.5Gb.
All worked flawlessly in DMA mode2 and UDMA on the UDMA capable ones.
3) Late Maxtor drives reported OK, DMA mode2 and UDMA.

- Intel FX, VX, HX, TX: all OK from personal experience.
- SiS 5597/98: OK, but must keep the PCI clock at 33 MHz.
- Apollo: reports indicate it works fine.
- Promise card: OK
- Others: OK AFAIK

- Most recent BIOSes should be OK, old ones should be flashed over with new
versions if available

>Linus what drives do you have reports for, and ditto the rest of the list
>(again I'll collect and summarise]

People in need of more information can check my Jumbo patch for kernel 2.0.35.
It includes a large doc file /Documentation/udma.txt. Also Mark Lord probably
has more data on drives that work/don't than anybody else.

Andrew D. Balsa

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