For those of you that already know this, please forgive me. I though it might be usefull to some. Checking to see if dma is enabled in windows device manager is useless, windows lies!!!!! I have been going nuts trying to figure out what is wrong with my computers. It was happening with three burners on two computers. I had checked and checked and checked again in device manager and I had use dma if avalable selected on all devices for both channels. Further, under current transfer mode, windows did in fact report that it was running multi word udma mode 2 (or something like that). Doing a burst rate test only gave 13-14mb/s on all 3 drives. I could not read or write over 10x. I had remembered enabling udma a long time ago. The main computer I was working on boots very fast. I had to reboot 5 times before I found it and there it was. Channel 2 was running in pio4 (that's what was being reported during startup). Windows was still saying that it was running dma. I was farmiliar with dma setting in windows and the bios but trusted what windows was reporting.
I remember having reset the bios to default settings after some overclocking problems. Aparently default settings for nvidia nforce2 based motherboards includes setting transfer to pio (it hapened on both my computers with diffrent brands of motherboards).
I have asked about dma settings and searched for threads on it and a moderator even pmed me with a link to a thread on setting it and nowhere is it mentioned to check the motherboard bios (I was going nuts trying to figure it out). Once I enabled dma in the bios, the burst rates went up to 26mb/s for two drives and 40mb/s for the third.
this may be specific to nvidia nforce 2 motherboard (and maybe not) but windows does not always report your dma setting corectlly.
The moral of the story, if you are having problems where dma is suspected, always check your bios (even if you thought you set it to enable udma) and don't trust what windows is reporting. Hopefully this will save some of you the headaches I have been having latlly.