A2091 SCSI Controller ZuluSCSI Hard Disk 2MB RAM per Amiga 2000 2000HD 2500 4000
You can read about the ZuluSCSI here Commodore Amiga A2091. Commodore Amiga 2000, 2000HD, 2500, 3000, 4000. Commodore Amiga 2000 or 4000 Computer. All Amiga Hardware Amiga Software NewTek Video Toaster.