XPost: alt.folklore.computers, openwatcom.users.c_cpp
From: ldo@nz.invalid

On Tue, 4 Nov 2025 09:39:41 -0700, Peter Flass wrote:

> I was thinking, are there any segmented architectures today?

Two different meanings of segmentation. It is possible to use segmentation
in a flat address space, as a memory-management technique. Think paging,
but with variable-length pages. (E.g. Burroughs machines did this. Also
think of how program code on the old 680x0-based Macintosh machines could
be divided up into individually-swappable “CODE” segments.)

The trouble was, such a scheme was prone to fragmentation, where the total
free memory might be larger than the segment you want to load, but it’s
broken up into discontiguous pieces that are too small to use. This is why
paging was preferred instead.

But now, with 64-bit architectures commonplace, you have multi-level page
tables. Think of these as a form of segmentation, where each segment is
made up of whole pages.

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