Source : Free On-Line Dictionary of Computing

Zilog Z280
     
        An 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 code}s (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).
     
        (1994-10-31)