It replaced the 16 MHz Motorola 68020 CPU and 68881 FPU of the II with a 68030 CPU and 68882 FPU (running at the same clock speed); and the 800 KB floppy drive with the 1.44 MB SuperDrive (in fact, it was the first Mac to have one).
Macintosh | Macintosh II | Macintosh 128K | Miss MacIntosh, My Darling | Macintosh File System | Tammy MacIntosh | System 7 (Macintosh) | Power Macintosh 8500 | Macintosh SE | Macintosh IIvx | Craig MacIntosh | Macintosh Toolbox | Macintosh Quadra 950 | Macintosh Plus | Macintosh IIx | Macintosh External Disk Drive | Macintosh (computer) | Macintosh clone | Macintosh Classic | Macintosh 512K | Charles Macintosh |
The first Macintosh model to include a SuperDrive floppy drive was the Macintosh IIx (1988).