Originally Posted by Toni Wilen
All SCSI controllers based on 53C7xx, 53C8xx are always true DMA. DMA controller is chip built-in. (A4000T, CSPPC etc..)
DMA does not have any "native" speed limit, it is controller, interface and memory bandwidth specific. EDIT: CPU upgrades rarely increase DMA controller speed because limit is DMA controller hardware, not CPU. (vs PIO controllers).
53C7xx (not), 53C8xx are PCI chips and AFAIR Amiga have no PCI (not sure if PCI<>Zorro is made in fully 'DMA' like way).
Most DMA SCSI in Amiga use original CSG chips as MC68K bus was not so popular on SCSI IC's market (so most of pre PCI DMA capable SCSI are focused on x86 bus).
And yes, i agree - DMA controller emulate CPU (from BUS perspective) so it is limited in same way as CPU.