On 23 Aug 2007 at 17:20, Mr Ian Primus wrote:
   Zilog Z8442BPS
 Serial I/O controller
  Zilog Z8430BPS 
 Counter timer circuit
 
It's been a long time--but didn't the "vintage" chips have legends
such as "Z80-SIO" and "Z80-CTC" as well as "Z80-CPU"?  I
liked that
convention--didn't leave much to the "I wonder what the heck this
chip does" mindset.
Cheers,
Chuck