[TUHS] Zilog Z80 Unix

Noel Chiappa jnc at mercury.lcs.mit.edu
Thu Apr 20 22:34:09 AEST 2017


    > From: "Erik E. Fair"

    > I have a memory of having seen a Zilog Z-80 .... based Unix, possibly v6
    > ... I recall asking the people in the booth how they managed without an
    > MMU, and don't recall their answer. I do remember thinking that since
    > Unix had "grown up" with MMUs to stomp on obvious pointer mistakes, the
    > software ought to be relatively well-behaved

I don't know about the Z80 part, but for the MMU aspect, recall that the first
couple of versions of PDP-11 Unix ran on a model (the -11/20) which didn't
have an MMU (although, as mentioned before here, it apparently did later use a
thing called a KS11, the specifications for which seem to be mostly lost).
Although recall the mention of calling out "a.out!", as to the hazards of
doing so...

And of course there was the 'Unix for an LSI-11' (LSX), although I gather that
was somewhat lobotomized, as the OS and application has to fit into 56KB
total.

So it was possible to 'sorta kind-of' do Unix without an MMU.

   Noel


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