Limit DMA Mode

[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!

 

[Pavel A.]

The registry hack to set DMA mode was posted in thread
Hard Disk DMA, advice ? help please.

on Nov, 21 . Or use this direct link - --

 

[Guest]

Depending on what youre hardware consists of,if its intel,go to thier web
site,
downloads,chip set software,locate the application accelerator and install
it.
You can adjust both UDMA and PIO modes as you like,however the best setting
i've found is "no limit".

 

[Adam Butler]

Thank You!
All I could come up with via Google was people wanting to enable DMA but I
couldn't find crap about reducing it!
Due to my Google searches I never even dreamed it would have been a subject
of a post here!
I'll play with this.

 

[Adam Butler]

Not Intel unfortunately.
VIA.
I do have all the latest drivers and also checked the HD manufacturer site
for a dma utility but none for this laptop drive.
I'm going to play with the link Pavel A. gave me as that looks promising to
limit my upper mode.

 

[Adam Butler]

Update - This did the trick!
I can now select Udma 4 or 2 and XP won't resort to 5.
4 seems to be working great. I've had zero lockups like dma mode 5 caused.

I don't know what does not like dma mode 5 (hard drive or the controller)
but it is now happy at 4 or below!

 

[Frank]

This is a Compaq thing....

 

[Guest]

Hi,

I would suggest you to go to compaq website to download and update to the
latest BIOS and chipset drivers.

Peter

 

[Adam Butler]

I agree Frank.
However Compaq would only tell me to run the system restore cd. Useless to
me as it is XP Home and I need Pro for domain membership. So, Compaq won't
help.
But, thanks to someone in another group I was able to identify and change a
registry key that will limit XP to a certain dma mode. I was able to change
my default dma mode 5 to 4 and now the old Compaq is running very well. It's
only been running about 24 hours but at mode 5 it would have frozen up at
least once or more per hour.
So I'm happy!