Limit DMA mode to 2 or 4?

[Adam Butler]

Hello,
I have a Compaq US700 laptop that does not like XP's choice of UDMA mode 5.
System freezes often.
So I set it to PIO mode only and then system is very stable but very
sluggish. Even the sound stutters when in PIO mode.
So my question is, can a registry change force XP to only use say UDMA mode
4 or less or even just mode 2?
Anything below UDMA 5 (UDMA 100) would be worth a try for me.
The BIOS on this laptop is almost useless. It offers no options to limit or
turn on/off dma for the ide controller.

Thanks for any suggestions!

 

[Adam Butler]

Problem fixed with this info:

Edit the registry:

HKLM\System\CCS\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}

0000 - IDE controller itself,
0001 - primary channel,
0002 - secondary channel.

Both channels, dwords:
MasterDeviceTimingModeAllowed 0xFFFFFFFF
SlaveDeviceTimingModeAllowed 0xFFFFFFFF
UserMasterDeviceTimingModeAllowed 0xFFFFFFFF
UserSlaveDeviceTimingModeAllowed 0xFFFFFFFF
and
MasterDeviceTimingMode 0xFFFF or 0xFFFFF
SlaveDeviceTimingMode 0xFFFF or 0xFFFFF
or
for Multi-Word DMA Mode 2 and PIO4 (burners, very old HDDs...) - 0x0410
for Ultra ATA33 (CDROMs, DVDs, old HDDs...) - 0x2010
for Ultra ATA66 (just HDDs) - 0x8010
for Ultra ATA100 (modern HDDs) - 0x10010
for Ultra ATA133 (ultramodern HDDs) - 0x12010

If the drive performance is unstable, OS locks it in one of the lower DMA
modes or in the PIO mode at all. The values "User...ModeAllowed" should
overcome this default behaviour.

Install Intel Application Accelerator.