1. zilog z280an enhanced version of the zilog z80 with a 16 bit architecture, introduced in july, 1987. it added an mmu to expand addressing to 16mb, features for multitasking, a 256 byte cache, and a huge number of new op codes (giving a total of over 2000!). its internal clock runs at 2 or 4 times the external clock (e.g. a 16mhz cpu with a 4mhz bus)