2MB RAM Amiga 500 chip RAM mod

Warning

Only attempt modification of your Amiga if you have the correct tools and are confident in your soldering skills.

Information

This page describes how to modify your Amiga 500 to get extra chip RAM and slow/ranger RAM at the same time with the BooBip 2MB upgrade.

Revision 5 (and later) Amiga 500 motherboards have JP2 which is near the CPU. This jumper in combination with EXTICK changes the position of expansion memory in the memory map between slow RAM and chip RAM. The logic on the BooBip 2MB upgrade can output a signal to allow both chip RAM and slow RAM at the same time. 512KB (0.5MB) of the memory is then used as extra chip RAM.

With this mod all 2MB of the upgrade memory is accessible, 1.5MB as slow/ranger RAM and the remaining 0.5MB as extra chip RAM.

Early machines came fitted with OCS (original chip set) Agnus chips. You will need an ECS (enhanced chip set) Agnus chip. Revision 5 boards can be upgraded to use an ECS Agnus. Please see the forums for more information.

Requirements

  • Amiga 500 revision 5 or 6A
  • Kickstart 1.3 (or later)
  • 1MB ECS Agnus already fitted
  • BooBip 2MB memory upgrade & Gary adapter

Mod

Note: route the wire to fit through the gap between the upper and lower RF shielding.

  1. Carefully cut the track between the bottom two pads of JP2
  2. Solder a jumper wire to the centre pad of JP2
  3. Connect the jumper wire to pin 1 of J3 on the 2MB memory upgrade
  4. Leave J3 pin 2 unconnected (Amiga 500+ only)
  5. Connect the Gary adapter following the 2MB upgrade installation instructions

Images

JP2

2MB-a500_mod.jpg

Memory board connection

2MB-a500_mod2.jpg

Installed

2MB-Installed_a500.jpg

Testing

Test with Keir Fraser's SysTest (or your favourite) memory test. Run avail from the Workbench shell to confirm the correct memory configuration is being detected.

More information in the 2MB memory upgrade installation instructions.