UDMA switching to PIO under WinXP?

[Mr Grumpy]

On my secondary IDE channel I have a Pioneer 104 Writer (configured as master) and Pioneer 117 DVD-ROM (configured as slave), both with the IDE channel settings defined in WinXP SP1 as "Use DMA when available".

Every now and again, the DVD-ROM switches itself to be PIO only and dramatically reduces the read speed.

The only way I've found of sorting the problem it is to remove the IDE controller ifrom Device Manager and let it reinstall itself on reboot. This cures it and it may last for a few days to several weeks before happening again.

Does anyone know what causes this? And how to stop it? It's a bit of a pain to have to uninstall/reinstall the IDE channel every time it happens

I don't know if it's relevant, but my mobo is based around a VIA chipset, with the 4-in-1 drivers from about 2 months ago (I've heard of a few "issues" with the latest ones). Other information about my setup can be found in "Computer Details".

Sorry, I know this is not strictly on-topic, but there is a DVD Writer on the IDE channel

[MassamBulla]

Correct me if I'm wrong anyone but I think in XP there is a built in sequence for controlling IDE devices. With that I mean, in the case of a CD rom reading a CD or DVD, if the disc in question has a few scatches making it hard to read, XP will attempt to read as normal for a number of times but if it is still struggling will step the IDE speed down in stages. Whatever speed it ends with is the the one that becomes permanent. The only way of returning to full DMA speed is to do as you have done.

[Remco]

Interesting...

I was wondering why my WinXp + Sp1 install was doing that.
This would qualify as a 'bug' to me!!

[Remco]

The whole thing depends on a registry setting. I write below how to correct it without having to unistall the driver and no need for reboor.
Open registry editor
Go to
"HKEY_LOCAL_MACHINE\SYSTEMS\CurrentControlSet\Cont rol\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}"
The Default Value should be "IDE ATA/ATAPI controllers"
Go to "0001" key if your device is on Primary IDE Chanel or "0002" if your device is on Secondary IDE channel
and change the MasterDeviceTimingModeAllowed or SlaveDeviceTimingModeAllowed to 0xffffffff depending if your device is master or slave
close registry editor.
Go to device manager select "IDE ATA/ATAPI controllers" and the corresponding IDE chanel go to "Advanced Settings" Tab and Set Transfer Mode to PIO and then to DMA if available again
That's should do it.

PS.As far as I know if XP have problem with the UDMA of a device they change it to PIO for better compatibillity.Haven't found a solution on how to disable that feature

To be more specific, WinXP drops the device out of UDMA mode and into PIO mode if it detects transfer errors on the device. Honestly, this isn't some feature which you would want to disable cause it can very much save you some future headaches which may occur due to data corruption. Instead of just outright disabling this feature, what you should do is make sure you've updated your chipset drivers if you are using a motherboard with a via chipset, and also change out your IDE cables since the cable itself could be causing the problem.

Use this solution at your own risk!! No whining about data corruption please

[kitty]

If you have the Intel Application Accelerator then it tends to hide some DMA settings. I uninstalled it and got back some control & no problems. Might go to the Intel site & see what the heck that proggie was supposed to do.

[Mr Grumpy]

Thanks Remco - that post you found looks interesting

I'll try the new Via drivers and IDE cable first before sinking to the reg fix

Grumps.

[Alnath]

Check for an updated BIOS for your mobo as well as this problem only effects certain chipsets, my old mobo with the KT 133a chipset used to do it until a BIOS came out that altered the registers, this with updated 4 in 1s sorted it out.

[MOVIEGEEK]

This is a common XP bug that affects all chipsets.I've encountered it once on XP but never on WinME or 98SE.
I give credit to "flaystus" for pointing out the remedy(remove,reboot).