I have a MEGA mini computer running WinXP Pro, 2.8 GHz, 1 GB memory, 2 hard drives (250 GB master & 500 GB slave set on cable select) and a NEC ND-3550A DVD drive (set up as master, not cable select). The DVD drive dropped down to PIO and I had to use the VBA script to reset it to DMA, no other method worked. The VBA script reset it to Ultra DMA, Mode 2 which is probably correct. Everything seems to be working fine now.
Now my question:
I was looking at three new Acer computer at work, all XP Pro, and checked the DMA settings on them.
Oldest (4 months old): The DVD drive(CD burner & DVD reader) was set on Ultra DMA, Mode 4, the HD was set on Ultra DMA, Mode 6
Next (2 months old) The DVD drive (DVD burner & reader) was set on Ultra DMA, Mode 2, the HD was set on Ultra DMA, Mode 5
Newest (1 month old): The DVD drive (DVD burner & reader) was set on Ultra DMA, Mode 4, the HD was set on Ultra DMA, Mode 5
What in the computer determines the different DMA modes? Is it the drive(s), controllers, motherboard or? Can the Mode be changed? What is the benefit of having a higher Mode on a DVD drive, if any?