Steve Nickolas has posted a patch which fixes the Apple II game Cubit on the Laser 128 computer. Cubit was a 1980’s clone of the popular Arcade game Q-Bert and was long the bain of those users who purchased the Video Technology produced Laser 128 Computer. A single memory location jump was causing the game to stop mid-stream as explained by Steve below:
My experience has been Cu-bit breaks on a Laser due to firmware
incompatibilities because it jumps to an undocumented entry point.
It’s a one-byte patch.
78D8- 4C 76 40 JMP $4076
78DB- CA DEX
78DC- E0 00 CPX #$00
78DE- D0 EB BNE $78CB
78E0- 4C A4 76 JMP $76A4
78E3- 20 33 FB JSR $FB33 <– derp!
78E6- 20 58 FC JSR $FC58
78E9- A9 02 LDA #$02
78EB- 20 C1 FB JSR $FBC1
78EE- A0 00 LDY #$00
78F0- B9 AC 7A LDA $7AAC,Y
On the Laser, that JSR causes the code to go off into lala land.
The fix is to change that line to 20 2F FB (JSR $FB2F), which does the
right thing on both Apples and Lasers.
The game is playable on the Virtual Apple II website at: