Unix for 8080/Z80? [Re: WooHoo!! PC/XT Unix anyone?]

From: Allison J Parent <allisonp_at_world.std.com>
Date: Sun Jan 24 13:58:39 1999

<On Sat, 23 Jan 1999, Allison J Parent wrote:
<> Unix didn't always have the idea of virtual memory. See Minix for an
<> example of that also V4 and maybe V5 unix didn't either.
<
<I would expect that the original PDP7 that ran UNIX didn't have VM...

No it didn't. I'm fairly certain that VM didn't appear until V7 on pdp-11
or maybe later.

The fact of the matter is there have been 8bit unix impmentations. The idea
that there is only 64KB is just means more reliance on things like overlays
or paging/swapping. Also many of the mid 80s 6809 and z80 system had some
kind of MMU to support large address spaces. The Z180 was good for 1mb with
it's MMU and most of the paging schemes for s100 permitted anyware from 512k
to 16mb. the late z280 allowed 16mb space using a paged MMU and added I&D
space along with user/system spaces. The latter I&D space (instruction and
data spaces) were features only found on the upper models of PDP-11
(11/44,11/45,11/60 and 11/70 and the J11 chip based systems 11/73 and
11/83). With I&D space and user/system space VM was supportable.

Allison
Received on Sun Jan 24 1999 - 13:58:39 GMT