This repo contains Kicad sources for a Static RAM expansion board for Sharp X68000 personal computer.
The expansion is implemented using 2MB static RAM chips to make the design simpler.
Address decoder is implemented using a ATF22V10 GAL chip. Source code for it is available in gal/ directory.
Board dimensions are taken from the midori project.
The board can support up to 8MB of memory and assumes you already have 2MB built in.
A fourth address line is routed and the board can support 1MB systems by masking half of the first memory chip. However, the GAL equations are not written for this case. Let me know if you have such a system.
I have tested it on a X68000 Expert system.
Users have reported success with XVI and ACE as well.
You can compile .pld GAL equations using GALasm.
I use JLCPCB with the following options:
- PCB Thickness: 1.6
- Surface Finish: ENIG-RoHS
- Gold Fingers: Yes
- 45°finger chamfered: Yes