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SubjectRe: SCO: "thread creation is about a thousand times faster than on
---------  Received message begins Here  ---------

>
> On Mon, Aug 28, 2000 at 06:52:18PM -0400, Alexander Viro wrote:
> >
> >
> > On Sun, 27 Aug 2000 yodaiken@fsmlabs.com wrote:
> >
> > > Again, it's a possible, but pointless feature. You want fork/exec
> > > in the presence of a file system and memory protection. But since
> >
> > Funny. I didn't know that -11/20 had memory protection...
>
> PDP-11 had good memory protection. I think PDP 8 may even have had it.
> None of this newfangled paging b.s. though.

Yes and no. It depends on which system you had. If memory serves:

11/05 - no
11/10 - no
11/20 - optional (not usally provided)
11/30 - optional (depended on configuration)
11/35 - included (may have been optional)
11/40 - included (may have been optional)
11/45 - included (all versions higher than 45 included MM built in)

Then there are the LSI versions:

LSI 11 - no
LSI 11/34 and higher - yes (11/34M equivalent - the M was memory management)

In the PDP-11/45 (the first version to have MM) memory management was an
add-on capability and was available without.

Many of these systems were used in embeded configurations. The PDP-10 used
an 11/20 as an IO/communications controller, and had an optional mm unit
to be able to address the 18bit range of the PDP-10 (and DecSystem 10).
It was optional because the PDP-10 didn't always have the memory that would
demand it.

The 11/30 was used in some aircraft equipment.

The 11/40 was used where the embeded system needed floating point. I think
that was in custom autopilots (not seen often).

-------------------------------------------------------------------------
Jesse I Pollard, II
Email: pollard@navo.hpc.mil

Any opinions expressed are solely my own.
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