[TUHS] Unix & Memory Management Units (MMU)
jnc at mercury.lcs.mit.edu
Thu Dec 8 06:12:03 AEST 2016
> From: Clem Cole
> DEC's Custom Special Systems (CSS) group .. build a simple base/limi
> register device, soon after the 11/20 was released.> ... So an early
> version of after the original 11/20 port from the PDP-7 had this
Oh, right, I'd forgotten about that: the KS-11 - I've previously enquired to
see if anyone had _any_ documentation for this, but so far, nada.
> I would look at Warren's First Edition work to see if there were dregs
> of this in that code base
Alas, I'd already had that idea (to try and at least re-create a programming
spec, at least, for the KS11). There do not seem to be any traces there,
perhaps because that code came from a document entitled "Preliminary Release
of Unix Implementation", which argues that it's a very early 'version' of V0
(the early 'versions' weren't very formal, there was a continuous process of
change/improvement going on, apparently).
> It is also noted that the 45 class system (45/55/70/44) had "17th"
> address bit - i.e. split I/D space. I believe that this is when "magic
> numbers" were really introduced so that could be supported.
No, they came in first for 'pure text' (0410):
which I would expect arrived to minimize swapping on machines with small
amounts of real memmory.
Support for user split-I/D (411) didn't arrive until Version 6:
although IIRC split I/D in the kernel was supported supported slightly
before it was in user - although V5 didn't:
so it couldn't have been much earlier than V6.
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