The DMAC controls part of the onboard SCSI found in the A3000 series machines, and the A4000T. DMAC 02 is usually used with Ramsey 04 and Dmac 04 is usually used with Ramsey 07. You can't mix them up.

Chip Name	Part Number	Used In
DMAC	390563-01	A590, A2091
DMAC	390563-02	A3000
DMAC	390563-04	A3000T, A4000T
Super DMAC	390537-02	A3000