Double-sided 1541 with an MFM controller and fast serial. Powers up in slow serial mode; only a C128 makes it fast.
| Chip | Where | Role |
|---|
| 251828 (64H156) 40/42-pin gate array | U6 | Read/write, byte-ready, sync, stepper phases, serial ATN acknowledge and CPU clock select (1541B/C, 1541-II, 1571) |
| WD1770 / WD1772 floppy disk controller | U11 (WD1770 or WD1772, $2000-$2003) | Single and double density floppy disk controller with built-in data separator and write precompensation. |
| 6522 VIA | U9 serial ($1800), U4 disk ($1C00); 65C22A CMOS parts | Two 8-bit ports, timers, serial and user port |
| 6526 CIA | U20 (6526A or 8520; fast serial at $4000) | Keyboard, joysticks, serial, user port |
| 6502 / 65C02 CPU | U1 (6502A) | CPU |
| 251829 (64H157) 20-pin gate array | U5 | Address decoder (ROM, RAM, I/O selects), saddle canceller and motor-speed PLL (1541B/C, 1571) |
| 23256 mask ROM 32K x 8 | U2 (DOS 3.0, 310654-03 / -05; pin 1 VPP tied to +5 V) | 32K x 8 mask ROM in the 27256 pinout. |
| 6116 2K x 8 static RAM | U3 (2016) | 2K x 8 static RAM. |
| 7406 hex inverter buffer/driver (open collector) | U8, U16 (schematic 310420) | Serial bus line drivers (CLK, DATA, ATN acknowledge), stepper phase and LED drivers |