U2/U3 rules ROMs decide which system a CPU board runs
U2 and U3 hold the operating "rules" code and differ between System 80 and 80A, so a board moves from one system to the other only after U2/U3 are changed. They are masked 2332 ROMs: soldered in on System 80 boards, socketed on 80A boards. A failed masked ROM can be replaced by an EPROM using the same conversion.
Systems
Related tips
- Which System 80 CPU board goes with which games
- Making a System 80B CPU board run an earlier game (or the reverse)
- System 80 CPU board main chips
- System 80 and 80A CPU boards swap only with the matching U2/U3
- Reading the System 80 CPU DIP switches
- How a 2332 rules ROM differs from a 2532 EPROM
- System 80 CPU board revisions D102, D107 and D20869
- Converting a D102 CPU board to take a 2716 game ROM
Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part Two, Clay Harrell (pinrepair.com)