Commodore 2090(a)

Commodore A2090
-Full length Zorro II Card
-Does not support autoboot (A company called Combitec did make an additional board to allow autobooting from this card)
-Also known as the A2500 Hard Disk Controller
-Known as the A2094 in rare occassions (not 2090a)
The 2094 is actually a Hard Disk kit which came with a 2090 autobooting HD Controller, a 3.5" 40MB HD, cables, mountings, ROMs, manuals and disks.
(Thanks to Arne Lunde)
-ST506 (IBM XT MFM) Controller
-Standard SCSI controller
-Zilog 80B Processor
-In Zorro III machines, all drivers and buffers must be loaded into CHIP RAM

Commodore A2090a (The above plus...)
-Has 2 ROMS (u50 & u51) which the A2090 does not have, to allow it to autoboot, although it uses it's own custom booting method and does not use the standard commodore Rigid Disk Block system. In order to prep and format a hard drive, you require a special prepping utility. NB. Some boards were actually sold without the ROMs but can be upgraded
-You can not have partitions larger than 256MB without a patch. Probably applies to the A2090 also.
-You need at list Kickstart 1.3 to autoboot

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


***PLEASE NOTE THAT SOME PARTITIONS MUST HAVE THE FOLLOWING NAMES***

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.