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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.minix
Subject: Re: Free Software Foundation (was: Re: Mach, the new standard?)
Message-ID: <29934@sun.uucp>
Date: Sat, 3-Oct-87 23:57:07 EDT
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Posted: Sat Oct  3 23:57:07 1987
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> I believe that certain micro-Vaxen _didn't_ actually have enough support to
> handle virtual memory as well as, say, a PDP-11/70.

Micro-*VAXen*?  As far as I know, the MMU on all VAXes is the same.  Did you
mean micro-PDP-11s?

> Might sound a bit simple, but for all it's greatness, the 68000 and 808[86]
> can't handle virtual memory because in the general case, an instruction can
> not be restarted.

Well, there *are* ways of doing virtual memory without that kind of support; I
think both Apollo and Masscomp did it with two 68000s, one of which was halted
in mid-bus-cycle when it referenced an invalid page.  The other one would then
wake up and fetch the page, and let the original one continue its bus cycle
when the page had been read in.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com