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From: lawitzke@eecae.UUCP (John Lawitzke)
Newsgroups: comp.unix.wizards,comp.arch
Subject: FSF
Message-ID: <2748@eecae.UUCP>
Date: Wed, 16-Sep-87 15:29:05 EDT
Article-I.D.: eecae.2748
Posted: Wed Sep 16 15:29:05 1987
Date-Received: Sat, 19-Sep-87 02:04:15 EDT
Reply-To: lawitzke@eecae.ee.msu.edu (John Lawitzke)
Organization: Mich. State Univ., Elec. Eng. CAE Facility
Lines: 20
Xref: mnetor comp.unix.wizards:4280 comp.arch:2201

Subject: Re: Re: Free Software Foundation (was: Re: Mach, the new standard?)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.minix
References: <8490@think.UUCP>
> Hmm...seems to me that you could implement fork() on an 8086, if you
> used a small memory model and programs cooperated (didn't play with
> the segment registers).  The PDP11 didn't have virtual memory either,
> if my memory serves me.  To run multiple processes concurrently you
> need memory management, but not necessarily virtual memory.  To fork,
> you need some way of creating distinct address spaces.  You certainly
> don't need virtual memory.

However, the PDP11 (I used the 11/23) has a memory management chip
that chops memory into 8K pages. With the 8086 you'd have to figure 
out how keep one area of memory system writable only and in this area
keep track of used segments. Of course then you have 64K pages.......
Also, how could you force users not to write to segment registers?

-- 
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                                 ARPA: lawitzke@eecae.ee.msu.edu  (35.8...etc]t