CPU EPROM jumpers J4 and J5

J4 and J5 set the EPROM size at 5C. Laser War to Batman carry two EPROMs (27256 in 5C, 27128 or 27256 in 5B): J4 in, J5 out. Star Trek 25th to Batman Forever use one 27512 at 5C and nothing at 5B: fit J5 and remove J4. Check these whenever a CPU board moves to another game.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• CPU jumpers J4 and J5 set the EPROM size at 5C
• Full CPU jumper settings by board version
• Data East CPU diagnostic test EPROM
• Leon's Data East CPU test EPROM
• Bench-testing a CPU board on +5 V
• Two PIA exceptions when using the PIA test EPROM
• Program runs but the PIAs never respond
• CPU board versions 520-5003-01, -02 and -03

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part One, Clay Harrell (pinrepair.com)