Eight SIMM sockets.  Upgraded four SIMMs at a time.

When using 4MB SIMMs, this machine requires special SIMMs which have a PAL chip or Timing Compensation circuit.

ROMs not 32-bit clean.  To access more than 8MB of RAM, Mode 32™ software is required.

The Mac IIx  contains 256K ROMs, and an Apple 1.44MB SuperDrive.

Serial Port with the phone icon supports synchronous modems, with handshaking on both the output and input.

Sound output is 8-bit stereo.

Has an international power supply.