This model was introduced as an update to the original Macintosh II, replacing the 16 MHz Motorola 68020 CPU and 68881 FPU with a 68030 CPU and 68882 FPU running at the same clock speed.

[2] The 800 KB floppy drive was replaced with a 1.44 MB SuperDrive; the IIx is the first Macintosh to include this as standard.

[3] The Mac IIx included 0.25 KiB of L1 instruction CPU cache, 0.25 KiB of L1 data cache, a 16 MHz bus (1:1 with CPU speed), and supported up to System 7.5.5.

Apple's nomenclature of the time used the "x" to indicate the presence of the 68030 CPU as used in the Macintosh IIcx and IIvx.

Support and spare parts for the IIx were discontinued on August 31, 1998.