Nicked from
amiga-hardware.com:
The A590 is a hard drive controller which connects to the side expansion slot of the A500. It provides both a SCSI controller, and an XT controller. An XT Controller is the very old 8bit IDE standard (not to be confused with ST506). Whilst it uses the same 40pin IDE cable that modern IDE controllers use, you cannot use modern IDE drives with the XT-Controller because they are 16bit. You must use XT hard drives. These were only ever made up to about 80MB in size. There are several versions of the ROMs for the A590, Version 6 ROMs only allow hard drives up to 512MB in capacity. Version 6.6 and 7.0 ROMs have been reported to work successfully with drive sizes up to 9GB but you will need at least OS3.5 to use drives over 4GB.So it's both an 8bit IDE and a SCSI controller, life's full of choices
.
