KeithI modified the board so I could add a 2K monitor code at 3800:3FFF.
This requires:
- 4K EPROM (2732)
- pin 21 isolated from VCC and wired to A12 (not A11)
- U3C pin 9 being isolated from A12 and then tied to ground.
Upgrading to 4K EPROM
A project log for ZX81 hi-res graphics board G007
By Gary Keall. 256x192 pixels. Patches BASIC so you can PLOT(n,x,y) instead of USR(addr) calls.
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