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NEC V20 and CP/M

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    Hey, hey, I didn't mean to criticize anyone. Sorry, if it looked that way.
    I was just curious why back in these days -when CP/M still played a vital role- CP/M Plus or MP/M weren't so popular.
    There's no reason to feel urged now to retrofit anything.. Also, 22Nice is fine the way it is, imho.

    (My first CP/M machine had CP/M Plus, whereas my father used to use the previous versions..
    We still have got some old 1970s issues of "Popular Electronics" floating around, introducing that hot piece
    of software named Control Program/Monitor. )

    I wonder if Woz still gets questions about the Apple II.
    I don't know. But I bet some people keep asking him about the Apple I..
    Last edited by Jo22; May 30, 2019, 08:48 PM.
    "Time, it seems, doesn't flow. For some it's fast, for some it's slow.
    In what to one race is no time at all, another race can rise and fall..." -The Minstrel


      Compupro sold a decent number of units with MP/M. The price of $1000 might have been a bit daunting for wide spread use compared to the $175 for CP/M-80 or $300 for CP/M-86 let alone the $40 for PC-DOS. That was Compupro pricing in 1983; other vendors might have different prices.

      CP/M Plus had a good career but it was mostly with lower cost systems outside the US so got ignored in the US. Most of the interesting CP/M Plus software such as with the Amstrad were quite late to market and largely machine specific. Just as an example, see Clicking on the memory requirement will bring up lists of other programs needing that much memory. It is a fast way to see the 128k and 256k Amstrad penetration. Probably similar lists for other super CP/M computers but I have not found those yet.

      Woz gets interviewed every year about some aspect of the Apple II. As long as he enjoys doing them, good for him.


        When MP/M came out, I think it's a fair estimate that the most common "full up" machine had 64K of RAM; probably 4116 type DRAMs. MP/M would not have done well. There was no standard for bankswitching; everyone did their own thing. For example, on the Durango F85, we ran the top 6 bits of the CPU address through a Fairchild 64x9 bipolar SRAM--translation speed was a big issue as we were using a 8202 DRAM controller.

        That gave you up to 256K of memory space (we didn't use the 9th bit), mappable in 1K blocks. It was elegant and we used it to good advantage in our own software. It wasn't what MP/M was designed to use, although it was possible to use it--but then, we didn't design our system to run MP/M (or CP/M). We had our own multitasking OS.

        In short, this wasn't the era of standardized conventions, as you see in the PC or Mac world. There were some wild differences between vendors.

        For multitasking, there was also the one-CPU-per-user mode, as one might find on a Molecular system. The "master" CPU handled I/O, but otherwise, each user had his own 64K address space. In a bus-oriented system, such as S100 or Multibus, this makes a lot of sense. Again, not something that MP/M was designed to.


          Well, the "canonical" MP/M system would have been the Altos Sun Series 8000, later called the ACS 8000. With MP/M being available in 1979, and TI's first 4164's in late 1978, machines like the ACS 8000 (available late 1979) could have used 4164's......

          I once had an ACS 8000-10; I set up MP/M on it for use by my uncle's local TV repair shop, who used it until he sold it and retired in 1989. I don't recall which RAM it used right off hand, but searching on images of the ACS 8000, it would seem 4116's are in use; reference for a documented max RAM of 208k. (I count 13 columns of 8 chips; 13*8 chips = 104; 104 4116's = 208k.)

          The Altos 580 I have now has 192k, and it does use 4164's, but it has a much smaller PC board than the monster used by the ACS 8000-10, which completely covered two side by side 8-inch floppy drives.
          Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"