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DMA Again!

PostPosted: Mon Jan 20, 2003 8:20 pm
by Null

I know this topic has been way too talked about...
BUT... I suddenly noticed my CD-ROM was performig very poorly and checked if DMAs were OK. They weren't :(
My CDROM is now "Modo PIO" (PIO Mode) [strange it doesn't specify "4" :-?]
The thing is that I have this drive as a secondary drive to my HDD, and my CDRW is master to the second IDE channel.
I've read that deleting and resintalling the affected channel corrects it... but it's my primary channel (where my OS is).

Is it safe to delete my primary channel to correct this issue?
Can someone confirm that deleting the primery channel will result in Windows redetecting it at reboot?

Note: My hard drive and CDRW are DMA enabled.

Thanks for your help.

Re: DMA Again!

PostPosted: Mon Jan 20, 2003 11:22 pm
by cfitz
Null wrote:Is it safe to delete my primary channel to correct this issue?
Can someone confirm that deleting the primery channel will result in Windows redetecting it at reboot?

I haven't personally tried it, but others here have reported that this works. Have you read the FAQ on DMA problems with XP?

In addition to describing how to delete the offending channel and reinstall it and reporting that people have done this on their OS channel with good results, it lists one other procedure you can try that doesn't involve deleting the channel.

You might also want to try moving the CD-ROM to the secondary channel with the CD-RW.


PostPosted: Tue Jan 21, 2003 3:38 pm
by Han
Personally, I think deleting primary channel does not result in non working system. Windows will detect it back, since it's not physically erased from hard drive...

How to assign the redetect option to a master or slave drive only, check this thread.

PostPosted: Tue Jan 21, 2003 8:51 pm
by Null
I did as
Han wrote:Open the Registry (Start -> Run -> Regedit), find the key below and do the following:

HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ Class \ {4D36E96A-E325-11CE-BFC1-08002BE10318} \ 000x

Last four digits are likely 0001, 0002. Under those keys you will find MasterIdDataChecksum, SlaveIdDataChecksum.
Delete the value corresponding to your drive. It will make the OS to redetect the device DMA capabilities after reboot.
Note that for many older CD-ROM drives DMA can not be enabled in Windows 2000/XP.

And it worked.
Thank you all.

PostPosted: Tue Jan 21, 2003 9:07 pm
by dodecahedron
Null, can you be more specific?
can you describe exactly what you did, which registry keys you deleted or edited, and what is your (corresponding) hookup, that is what/how many drives, on what channel (primary/secondary) and master/slave arrangement.


PostPosted: Tue Jan 21, 2003 10:42 pm
by cfitz
Yes. It might make for helpful addition to the FAQs on DMA.


PostPosted: Wed Jan 22, 2003 12:16 am
by Null
I have my drives set up like this:

Primary IDE Channel
Master: SAMSUNG SV4012H

Secondary IDE Channel
Master: HL-DT-ST CD-RW GCE-8320B

They were all DMA enabled. The problem was that my CDROM switched to PIO mode (only the CDROM).
I ran regedit and navigated to the string:
Inside that you have four sub-levels:

In my case I have:
0000 for the VIA IDE bus main controller (dont know the exact translation for that [it's in spanish])
0001 for the Secondary IDE Channel (as you can read in "DriverDesc").
0002 for the Primary IDE Channel
Inside that one (0002) you can find several entries, I deleted one called "SalveIdDataCheckSum".
I rebooted and it was DMA again (I still had "DMA if available" marked).

I thought it was that entry I should delete because of what I read here:

Windows XP will turn off DMA mode for a device after encountering certain errors during data transfer operations. If more that six DMA transfer timeouts occur, Windows will turn off DMA and use only PIO mode on that device.

Feel free to ask, after all you've helped me a lot.

PostPosted: Wed Jan 22, 2003 12:17 am
by cfitz
Thanks Null. Very helpful. I leave it to dodecahedron to incorporate into the FAQs.