From: bc@freeuk.com   
      
   On 30/11/2025 14:26, Philipp Klaus Krause wrote:   
   > Am 30.11.25 um 14:10 schrieb bart:   
   >> On 30/11/2025 09:51, Philipp Klaus Krause wrote:   
   >>> Am 30.11.25 um 10:05 schrieb Michael S:   
   >>   
   >>>> * Zilog Z80 based MCUs   
   >>>   
   >>> This one gets complicated. The original Z80 had a 4-bit ALU, but is   
   >>> widely considered 8-bit, and I'd agree.   
   >>   
   >> That's news to me. Are you thinking of the 4040 as the original? Z80   
   >> was a souped-up version of 8080: a superset with better technical specs.   
   >   
   > Both the 4004 and the Z80 were designed by Masatoshi Shima. See this   
   > interview for details on the Z80 (he does call the Z80 an "8-bit   
   > microprocessor", just a few sentences before mentioning its 4-bit ALU):   
   >   
   > https://archive.computerhistory.org/resources/text/Oral_History/   
   > Zilog_Z80/102658073.05.01.pdf   
   >   
      
   OK, so the Z80 has a '4-bit pipelined' ALU. It's explained in more   
   detailed here:   
      
   https://www.righto.com/2013/09/the-z-80-has-4-bit-alu-heres-how-it.html   
      
   (It doesn't say why; presumably it uses fewer on-chip resources, or to   
   make a point of difference from the 8080.)   
      
   But that appears to be an implementation detail that is transparent to   
   the user.   
      
   Since it uses 8-bit registers, 8-bit instructions, and has an 8-bit   
   databus, I think it can pass for an 8-bit CPU!   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)