24 Jan
1999
24 Jan
'99
10:41 a.m.
Allison J Parent <allisonp(a)world.std.com> wrote:
No it didn't. I'm fairly certain that VM
didn't appear until V7 on pdp-11
or maybe later.
I'm fairly certain that VM didn't appear in ANY released version of Unix
on a PDP-11.
Only a few models of PDP-11 had the processor capabilites needed to support
VM (instruction continuation or instruction restart), and they were not used
in any commercial OS. It's been rumored that there were bugs that rendered
the capability unusable.
In any case, though, the PDP-11 only supported 8 pages of 8K bytes (or 8 pages
each of I & D space), which isn't really enough to make VM noticably superior
to swapping. A PDP-11 with 4M of physical memory could support around 30
maximum-sized processes resident in memory simultaneously.