A590, Front right
A590, Front left
A590, Rear
A590, base
Image of A590 box
- 860 x 658, 104K
Image of A590 box, open
- 1002 x 1142, 159K
Image of motherboard
- 2547 x 1707, 931K

The A590 is a sidecar unit for the A500(+).  It contains a hard drive controller and support for up to 2MB of AutoConfign FastRAM.  It provides both a 33C93A-based SCSI controller, and an XT controller. The XT Controller is the very old 8 bit IDE standard (not to be confused with ST506, or the 16-bit AT/IDE type). Whilst it uses the same 40pin IDE cable that more modern 16-bit IDE controllers use, you cannot use modern IDE drives with the XT controller because they are 16 bit. You must use XT hard drives. These were only ever made up to about 80MB in size. The A590 was usually shipped with a 20MB Seagate SCSI drive by default or a 20MB Western Digial XT drive, but the drive specifications are printed on the base of the unit.

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 or Amiga OS 3.1.4 to use drives over 4GB. XT drive support was also dropped with the 7.0 ROM set.  The GuruROM V6 is an upgrade option, but see the notes at the end of this page for additional infromation.  The SCSI2SD product is a viable replacement for failed physical hard disk units.

Notice the names of the LEDs on the unit, named Fred and Wilma.

DIP Switches

Switch 1
OFF: Disables Autoboot ROMs (Kickstart 1.2, no HD/game compatiblity)
ON: Enables Autoboot ROMs (Kickstart 1.3+)

Switch 2
OFF: LUN Disabled (One Drive at each address)
ON: LUN Enabled (Multiple drives at each address)

Note: Some SCSI drives such as certain Seagate and Epson drives, respond to more than one logical unit address (LUN). Such drives will appear on the Workbench screen and the Hard Drive Preparation, Partitioning, and Formatting screen in HD Toolbox multiple times, at the same Address but at LUN 0 through 7. If this occurs, set switch 2 to OFF.

Switch 3
OFF: Short wait period for drive to spin up. Parity checking enabled
ON: Long wait period Parity checking disabled for message in phase

Switch 3
Time-Out Length: If you are using a SCSI drive that takes longer than 30 seconds to start up when you turn the system on, such as some seagate drives, you may wish to set switch 3 to ON. When the switch is in the OFF position the time-out period, the time between power-on and when the system checks the drive, is short.

Switch 4:
Reserved (e.g., don't mess with it!)

Jumper Settings

Note: The A590 is shipped with all jumpers set to 1 by default


JP1 1 = Amnesia
2 = 512K
3 = 1MB
4 = 2MB
Sets the amount of RAM installed
JP3 1 = XT Drive
2 = SCSI Drive
Set LED for XT or SCSI Drive
JP4 1 = Interrupt 2
2 = Interrupt 6
Note: Do Not Change

The A590 is supported by the GuruROM V6, but important caveats exist:  
- The DMAC-01 chip, if present, must be updated to the -02 version (same as on the A2091, but possibly more common to A590's).
- The 14Mhz clock hack for the 33C93A SCSI chip is more complicated than on the A2091, and should only be attempted by a qualified technician.  This is needed for 'significant' speed improvements over the v7.0 C= ROM (i.e. SCSI Sync support), but not for device compatiblity improvements.
- The metal drive tray is likely to intrude upon the seating of the GuruROM module, so physical modification (or removal) will be necessary.
- XT drive support is dropped (same with C= ROM 7.0).
- The jumpers on the rear change function.

Page contributors: Andrew Bowers, Eric Schneider, Jan Pedersen, Konrad Popp, Mats Magnusson, Paul Gable, Peter Braechter, RiWa & Friends, Thomas Unger
Updated: 5/3/2019 . Added: 12/22/2004