MIT provides MULTICS source and documentation

[Brian L. Stuart]

> > >> But what machines could run the that today?
> > > 
> > > Anything you port it to.

The segmentation architecture would be hard to fake.  And
the idea of segments is so deeply ingrained, I doubt you'd
want to try.  However, the x86 does seem to have the necessary
segmentation structure.  Unfortunately, it's only got 32-bit
addresses.  Even in the 60s, the Multics machines had 36.

> > That's an interesting question.  I can't think of that many machines
> > with a hardware ring architecture, and it's not something that can be
> > easily faked with more traditional architectures.  It would be a fairly
> > invasive "port".
> 
> It pains me to say it, but you could just throw CPU horsepower and
> memory at the problem.

Yes and no.  In principle, the only thing you'd have to ensure
is that you gave control to the supervisor on a ring crossing.
So you could make all pages not in the current ring inaccessible.
On a page fault, apply the ring brackets in software and change
the page tables as a result.  At the very least, you'd take a
performance hit.

Having said that, somewhere in the back of my head, I want to
say that the x86 has at least part of the mechanism already.
So a port to it would be less painful than to a lot of others,
except of course, for the smaller address space.

Of course, I could be totally off.  I'm certainly no Multics
expert, and my memory of the details of the x86 segmentation
are rusty at best.

BLS