Honneywell multics? from panels. the inline phots in this message folks -smecc

Noel Chiappa jnc at mercury.lcs.mit.edu
Thu Mar 17 07:53:07 CDT 2016

    > From: Mouse

    >> simulating a segmented machine on a non-segmented machine, i.e. one
    >> with large unidirectional addresses (segmented being a
    >> bi-directionally addressed machine) - [...]

    > Hm, "unidirectional" and "bidirectional" are terms I'm having trouble
    > figuring out the meaning of here. You seem to be using them as,
    > effectively, synonyms for "non-segmented" and "segmented"


    > but I don't see any way in which directionality makes any sense for
    > either, so I can only infer I'm missing something.

Imagine a graphic model of the memory in non-segmented, and segmented,

The former can be modeled as a linear array of memory cells - hence
'uni-directional'. The latter can be modelled by a two-dimensional array -
segment number along one axis, word/byte within segment on the other - hence

Maybe 'uni-axis' or 'bi-axis' would have been a bit more techically correct,
but 'uni-directional' and 'bi-directional' were the first terms that came to
mind - and I didn't think of how they could be confusing (in terms of their
common meanings, when used for flows). Sorry!


PS: I'm trying to remember all my thoughts about simulating a segmented
memory with a large flat address space. One was that one can prevent pointer
incrementing from 'walking' from one segment into another by leaving a 'guard
band' of a few empty pages between each 'segment'. However, this points out
an issue with such simulation: one cannot easily grow a 'segment' once
another 'segment' has been assigned space above it.

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