[Gswiss]

Running under XP-SP2, when we use a single disk, DMA is active and everything is fine.

When we connect a second physical disk as slave on the same Main IDE Channel, both switch to PIO.

We bought a new 80-connector ribbon and tried several different slave disks. No change.

FYI, both dvd readers are on secondary channel.

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This may well be an issue with the drive you're adding if it changes to PIO mode as soon as you connect it.

[Neil Jones]

This may well be an issue with the drive you're adding if it changes to PIO mode as soon as you connect it.

[Gswiss]

Both disks change to PIO

[Neil Jones]

They will do because the second drive is dragging the first one down, especially if it itself changes as soon as you put the second drive in.

[Samm]

Actually there's no reason for that to happen so long as both hard drives support the same DMA modes & the cable is an 80 wire one, which it is. I would be tempted to blame it on the second hard drive but you said you've tried several different ones to no affect.

This problem can be caused by a bad IDE cable but as your one is new, this seems unlikely.

You may find it is a bios issue which can be resolved by a bios update. Alternatively, it could be a chipset/driver issue. It could even just be XP being flakey...

Do you happen to know exactly what motherboard you have?

[Gswiss]

The issue was solved a bit by chance. We went into the BIOS to see whether DMA could not be forced from there. As it turned out, we could not since we were faced with a Department Store Tower, nevertheless with a Gigabyte MB and AMI BIOS, 5 or 6 years old (Pentium 4, 1.7 Ghz).

It's at that point, in the BIOS, that we noticed that the two disks were set to User-defined. When we changed this to Auto, the problem was solved and everything was back to normal as it was before we ran into the defective connector issue which started all.

Thnaks to all for the suggestions which put us on the right track.

Edited by Gswiss, 20 June 2008 - 11:38 AM.