Eight SIMM sockets. Upgraded four SIMMs at a time.
Requires a PMMU (Paged Memory Management Unit) chip in order to enable memory configurations greater than 8MB. Motorola used to sell a PMMU chip called the 68851. It is no longer in production, and while they are exceedingly scarce, these chips can occassionally be found.
When using 4MB SIMMs, this machine requires special SIMMs which have a PAL chip or Timing Compensation circuit.
ROMs are not 32-bit clean. To access more than 8MB of RAM, Mode 32‚Ñ¢ and a PMMU are required.
The Mac II contains 256K ROMs, and an Apple 800K floppy.
Due to ROM irregularities, the Mac II, as shipped, can not accept 4MB or larger SIMMs in Bank A. This limits the maximum memory expansion to 68MB (four 16MB SIMMs in Bank B + four 1MB SIMMs in Bank A).
It is possible to put 128MB of RAM into a Mac II by installing the Apple FDHD upgrade which includes a high-density floppy drive along with a set of Mac IIx ROMs. The IIx ROMs remove the irregularities of the Mac II.
Serial Port with the phone icon In the Mac II supports synchronous modems, with handshaking on both the output and input.
