The onboard SCSI is not DMA and on my 4000T it refuses to work with HDD's...
The A4000T onboard SCSI is more or less identical to the A4091 SCSI, and is Zorro3 DMA.
Try fiddling with the switches on the back, the label seems to be backwards/up-side-down on mine, so you will want the switches in the opposite position of what the label says...
-Paul
