The June 1984 edition of Practical Computing magazine (page 43) refers to the American Microsystems Incorporated S-83 CPU as a Z80 compatible CPU with an 8K mask ROM capable of holding Digital Research's Personal CP/M. This feature, coupled with better dynamic RAM handling than the Z80 along with a non-multiplexed 16-bit address bus, could have resulted in very low chip count Z80 computers.

Apart from this one article, there's not much else out there about the S-83. Did it get used in real hardware, or was it (as I suspect) another puff of mid-80's vapour that never made it beyond a press release?

  • As an aside, enhanced chips were quite common, at least in the embedded world. I worked on Dallas Semiconductor CPUs that were basically Motorola 68000-family chips with extra stuff added to the top of the chip (like RTC or extra I/O). Why buy (and design for) N chips when you can get away with one? :-)
    – paxdiablo
    Feb 18, 2023 at 23:20
  • Also in books.google.com/… in InfoWorld
    – Jon Custer
    Feb 19, 2023 at 0:32
  • 2
    The Z80 already has a non-multiplexed 16-bit address bus.
    – Tommy
    Feb 19, 2023 at 13:21
  • 1
    The 1985 AMI MOS Products handbook has a "Preliminary Data Sheet" for the S83, with 31 pages laying it all out. However, the next data books I have found (1990 at bitsavers) have no mention of it. Perhaps vaporware, but they got pretty far down the road first.
    – Jon Custer
    Feb 20, 2023 at 13:53
  • @paxdiablo early SOCs?
    – RonJohn
    Apr 23, 2023 at 20:31

1 Answer 1


While I know about Personal CP/M, that S83 is new to me.

I would not expect Z80 nor CP/M to show up in personal computers (or any general available machines showing computer like features) as late as 1984, or since this was an announcement, even later. Also, wasn't 'persona# CP/M DR's offering for embedded systems? So the use case may be much like with DOS after ca. 1990 - embedded systems, which are always build from comparably simpel and more mature components. We did use Z80 for new designs way into the 2000s.

  • 3
    It didn't seem to stop Amstrad with their CPC and PCW machines: all released after 1984, and all (except the first CPC 464) supplied with CP/M
    – scruss
    Feb 18, 2023 at 16:23
  • Also the Commodore 128 in 1985, though let's face it ‒ neither was bought for its CP/M compatibility. Later, in the 90s, TI based its first family of graphing calculators on the Z80. Feb 18, 2023 at 18:26
  • KayPro was releasing new Z-80 systems in 1984.
    – RonJohn
    Feb 18, 2023 at 21:35
  • Nice list of systems, but they were all continuation of existing systems to feature an existing base, not a new design - and all of them on the way out.
    – Raffzahn
    Feb 18, 2023 at 21:40
  • 4
    Saying a Z80 was obsolete as a general personal computing CPU because there was the 80286 and 68000 is like saying a Core i5 is obsolete today because there are Threadrippers and comparable HEDT CPUs. An 80286 PC was COSTLY in 1985. Feb 18, 2023 at 23:12

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