2 IDE channels for a total of 4 UDMA100/ATAPI devices. UDMA100 appears to be have been selected for price/performance reasons as faster channels tend to add significantly to the cost without providing an equivalent performance increase. Anyone who wants faster devices should really consider SCSI anyway in my opinion.
As far as SCSI is concerned, this information was posted to an AmigaOne developers list by Ross Vumbaca and is reproduced here with his permission.