MIT provides MULTICS source and documentation
Brian L. Stuart
blstuart at bellsouth.net
Mon Nov 12 15:43:48 CST 2007
> > >> 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
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.
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