After rebooting Windows, Steve Brazelton wrote:
> Enabling DMA on scsi-emulated IDE devices can be a bit of a problem.
> I can think of two ways to do it. The first is to directly edit the values
> in
> /proc/ide/hdX/settings; where X is your specific device. I could never
> get enough info to try this. The second requires that the

OK, I solved the problem, and here is an explanation for the Google archive.

This problem occurs when you have an IDE cd/dvd burner using ide-scsi
emulation. Accessing the drive causes a heavy CPU load on the system
resulting in mouse jerkyness, the system clock losing time, etc. This
slowness can be traced to dma being off for the cd/dvd drive. hdparm
will not work on ide-scsi drives.

To check if dma is on for an IDE cd drive cat the file
/proc/ide/hdX/settings. There will be an entry using_dma. If it is
0 then dma is off. To turn it on run this command:
echo "using_dma:1" > settings
You *might* need to make ide-scsi a loadable module (not compiled in)
for this to work. I don't think you really need this, but I did it
so I mention it as something to try.

Thanks for all the help folks!