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Old July 30th 19, 06:25 AM posted to alt.comp.hardware.pc-homebuilt
T. Ment
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Posts: 87
Default PCCHIPS M811 IDE UMDA

The PCCHIPS M811 motherboard is known to have IDE UMDA errors at ATA-100
speed. Windows XP downgrades it to ATA-66 and that works. But DOS has no
way to downgrade it. BIOS can enable or disable UDMA per drive, but has
no option to limit the speed. BIOS just uses the highest speed the hard
drive reports.

https://forums.tomshardware.com/thre...v266ad.435007/

They advised flashing a BIOS from the similar ECS K7VTA3. I tried that,
but it didn't help.

For other reasons (to save an IRQ) I decided to put both IDE devices, a
hard drive and a cdrom on the same cable. Some people advise against IDE
slaves, but for a cdrom that gets little use, I don't see a problem.

Linux starts with the speed BIOS sets, but will downgrade when it gets
too many UDMA errors. It's hard to miss, it spits rude messages on the
screen. I have seen this many times.

But now, with both cable positions filled, the ATA-100 errors are gone.
I tried to cause errors with some large directory copying, which always
caused a downgrade before, but now, I get no errors at all.

Looks like filling both IDE cable positions somehow changes the cable
signaling to make this motherboard work right at ATA-100. But I have no
idea of the EE involved.

Just wondering if the experts do ...