ID #4254

Commodore: A2090 / A2090a / A2092 / A2094

Connection: Zorro II


A2090, Rev 5
A2090, Rev 5

Hi Res Version, A2090 - 366K
Hi Res Version, A2090, Rev 5 - 576K
Image showing A2090 ST506 connectors - 897K
Image showing A2090 SCSI connectors - 959K

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 is known by serveral names, but it is the same hardware. For example the SCSI controller supplied with the A2500 is simply this card. It was also known as the A2092 which was simply this card packaged as a "Hard Disk Upgrade Kit", including a 40MB hard drive for the A2000. To confuse matters further this "Hard Disk Upgrade Kit" was sometimes referred to as the A2094. The A2090a is simply this card, prefitted with auto-booting ROMS. 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. Bootable versions of this card 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. 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):

Contributions to this page by:
Benjamin Beloch, Calum Tsang, Dave Haynie, Sylvio Kurze

Letzte Änderung des Artikels: 2009-01-29 10:13
Revision: 1.0

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