Newsgroups: comp.arch
Path: utzoo!utgpu!jarvis.csri.toronto.edu!neat.ai.toronto.edu!ephemeral.ai.toronto.edu!bradb
From: bradb@ai.toronto.edu (Brad Brown)
Subject: Re: unconventional architectures
Message-ID: <89May7.001514edt.39763@neat.ai.toronto.edu>
Organization: Department of Computer Science, University of Toronto
References: <112@centaure.UUCP> <422@unicads.UUCP> <11579@cgl.ucsf.EDU> <89May6.165030edt.10782@ephemeral.ai.toronto.edu> <1989May6.234007.23517@utzoo.uucp>
Date: Sun, 7 May 89 00:15:07 EDT

In article <1989May6.234007.23517@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>In article <89May6.165030edt.10782@ephemeral.ai.toronto.edu> bradb@ai.toronto.edu (Brad Brown) writes:
>>Unfortunately, a machine like this can't run C very well, 'cause C presupposes
>>a flat, uniform memory space...
>
>Untrue.  (Consider all the C compilers for the revolting 8086 and its ugly
>descendants, which most definitely don't have a flat uniform memory space.)
>There would be problems in implementing C on one of those machines, but
>segmentation per se isn't among them.


But consider how C is implemented on the 8086 and it's brethren:  You simulate
a flat address space and give the programmer a bunch of different memory models
so they can decide how big their flat space is.  The point is that C wants to
be able to point anywhere in memory, more or less, whereas really segmented
machines like the Buroughs I was talking about get thier protection ability
from having a segment for each (more or less) object in the system.

I'm sure that C *could* be implemented on that machine, but the architecture
would get in the way.  I'm sure that C does not literally require a perfectly
flat address space, but it sure encourages it!

					(-:  Brad  :-)