The best seller. PLA and VIC-II run hot.
| Chip | Where | Role |
|---|
| PLA 82S100 | U17 | Address decode + bank switching |
| 251715-01 / 252535-01 memory controller (C64C) | U8 (250469 boards: 251715-01 on rev A, 252535-01 on rev B) | PLA, DRAM address multiplexer and chip selects in one chip (C64C short board) |
| 6567 / 6569 VIC-II | U19 | Video + DRAM refresh + CPU clock |
| 6510 CPU | U7 | CPU |
| 6581 / 8580 SID | U18 | Sound + paddle A/D |
| 6526 CIA | U1 (CIA1), U2 (CIA2) | Keyboard, joysticks, serial, user port |
| 4164 DRAM 64K×1 | U9-U12, U21-U24 | Main RAM (8 chips = 64 KB) |
| 4464 / 41464 DRAM 64K x 4 | U9, U10 (250466; U10, U11 on the 250469) | Dynamic RAM, 64K x 4. Main RAM on the BBC Master; reported on later 130XE boards. |
| 2114 SRAM 1K x 4 | | Static RAM (ZX80 and ZX81 1K) |
| 2364 Mask ROM 8K×8 | U3 (BASIC 901226), U4 (KERNAL 901227) | BASIC and KERNAL ROMs (C64); BASIC and KERNAL (VIC-20, PET); character ROM (C128) |
| 23128 Mask ROM 16K×8 | U4 (251913-01: BASIC and KERNAL in one ROM; 250469 boards only) | BASIC and KERNAL ROMs (C16, Plus/4, C64C short board, C128) |
| 2332 Mask ROM 4K×8 | U5 (character 901225) | Character ROM (C64, VIC-20, PET) |
| 8701 / 7701 clock generator | U31 (250425, 250466); U20 on the 250469 | Dot clock and color clock from one crystal (later C64 boards, C128) |
| Rail | Expect | Measure at |
|---|
| +5 V DC | +5 V UNVERIFIED | 6510 pin 6 (8500 on the 250469) |
| 9 V AC | About 9 V AC between the two 9 V AC pins (DIN pins 6-7) | c64-power pins 6, 7 (power DIN) |
| 9 V AC | About 9 V AC between the two 9 V AC pins (DIN pins 6-7) | c64-power pins 6, 7 (power DIN) |
| +12 V (VIC-II and 6581 Vdd) | About +12 V | VIC-II pin 13; SID pin 28 |
| SID supply (+9 V or +12 V) | About +12 V with a 6581, about +9 V with an 8580 | SID pin 28 |