The LaserWriter 12/640 PS printer comes with 4 MB of DRAM installed in one of its two SIMM slots. You can expand DRAM capacity up to 64 MB by using higher capacity SIMMs and populating both slots. The LaserWriter 12/640 PS has separate controller systems for imaging and I/O processing. The imaging system uses an AMD AM29040 processor, and the I/O processing system uses an 80C186 embedded processor. The imaging and I/O systems share messages and data through a shared SRAM (static RAM).
* [[Apple LaserWriter 4/600 PS Developer Note]]
* [[Apple LaserWriter 12/640 PS Developer Note]]