My bios settings are auto for all devices and also for Ultra dma .
my winxp settings primary ide ( I only use my primary ide )
Device 0 -tranfer mode DMA if available
Current tranfer mode \"Ultra dma mode 2\"
So there must be different modes of UDMA .
I only have one ide device (dvd)
In PIO modes there are 0 - 4 and 4 is the fastest mode .
Here is a link about udma in winxp from microsoft :
http://www.microsoft.com/hwdev/tech/storage/IDE-DMA.aspI hope this answers your question