in order to take advantage of system 7's virtual memory feature, a macintosh equipped with a paged memory management unit (pmmu) is required. the motorola 68030 cpu has one built-in, and one can be added to the motherboard of the motorola 68020-equipped macintosh ii. the other macintosh model using an 68020, the macintosh lc, cannot use virtual memory. apple introduced the 68030-equipped macintosh lc ii shortly after system 7's introduction. despite the newer processor, the lcii retained the earlier model's 16-bit bus and did not perform any faster than the lc it replaced.