The Motorola 68020 was the first 32bit Mac processor, first used on the Macintosh II.The 68020 had many improvements over the 68000, including an instruction cache, and was the first Mac processor to support a memory management unit, the Motorola 68851.. The Macintosh LC configured the 68020 to use a 16bit system bus with ASICs that limited RAM to 10 (as opposed to the 32bit limit of 4 GB).