Hi Res Version (954 x 356)

The A2090 is a full length Zorro II card which contains a SCSI controller and an ST506 (IBM XT MFM) controller. The card does not support autobooting, however there were solutions released which allowed the card to boot, such as the Commodore Autoboot Card or the Combitec AutoBoot Card (A2090b). This card may also have been known by a few other names such as the A2500 Hard Disk controller or the Commodore A2094. The A2094 is was actually a hard disk kit from Commodore, containing the A2090a, 40MB HD, cables, mountings, ROMS and manuals. The card uses the Zilog 80B processor. If you intend to use this card in Zorro III machines, then all drivers and buffers must be loaded into Chip RAM and not Fast RAM.

The Commodore A2090a is really just the A2090 with autobooting ROMs onboard. It uses its own custom booting method and ironically does not use the Commodore RDB standard which most hard drive controllers use. In order to prep and format the drive, a special prepping utility is required. You cannot have partitions larger than 256MB without a patch, and this probably applies to the A2090 also. In order to autoboot, you need at least Kickstart 1.3.

Board# Physical                 Size    Revision Number
U50 HI Top centre, below J2     28 pin  315098-01 2090  AB5C
U51 LO Top centre, below U50    28 pin  315097-01 2090  D32B
U36    Top right                28 pin  390230-09 2090a 2FEF

Connector/Jumper   Description
J0                 34pin ST506 Control Connector
J1                 20pin ST506 Data Cable Connector 1
J2                 20pin ST506 Data Cable Connector 2
J4                 2pin SCSI LED Connector for A2090
J4                 2pin Autoboot ON/OFF for A2090a
J5                 LED Connector
CN1                DB25F SCSI Connector
CN2                50pin SCSI Connector


Physical Device  | 2 Cylinder Section | Unit | First Partition
1st ST506 Drive  |      RES0:         |   1  |     DH0:
2nd ST506 Drive  |      RES1:         |   2  |     DH1:
1st SCSI  Drive  |      RES2:         |   3  |     DH2:
2nd SCSI  Drive  |      RES3:         |   4  |     DH3:
3rd SCSI  Drive  |      RES4:         |   5  |     DH4:
4th SCSI  Drive  |      RES5:         |   6  |     DH5:
xth SCSI  Drive  |      RES(x+1):     | (x+2)|     DH(x+1):

Thanks to Calum Tsang and Dave Haynie