What determines the ultra DMA mode level settings?

[ed klein]

Is the ultra DMA mode level settings determined by the optical drive itself or is the size of the CPU (resources) a factor to determine the ultra DMA mode setting level.

Current setup:
AMD Athlon XP 3200+
2191 MHZ
1.0 gb ram
All IDE cables are 40 pin, 80 leads

IDE connections:
primary IDE master Plextor 760A (ultra DMA mode 4)
primary IDE slave Vacant

secondary IDE master Plextor 708A (ultra DMA mode 2)
secondary IDE slave Vacant

SATA connections;
primary 120 gb hard drive
secondary Plextor 716SA (ultra DMA mode 6)

[Chewy]

dma was developed to relieve cpu use during transfers, it's handled by the
ide controller chipset so cpu speed does not impact dma significantly.
DMA 2 at 33MB/s exceeds any sustained transfer from any optical drive.
At 33MB/s we are talking 24X burn or read speeds, kind of hard to get the disks spinning that much faster, on that sata drive I wouldn't even want to be in the same room with it trying to spin 5 times faster.
Now burst over interface is another story, the dma 4(100MB/s) will give you an extra 66+MB/s, but the cache on the drive will only hold 1/30 of a second's transfer.

smoke and mirrors but sounds nice