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>From JSol@RUTGERS Tue Oct 27 19:30:41 1981
WorkS Digest          Wednesday, 28 Oct 1981        Volume 1 : Issue 25

Today's Topics:        MC68000 Paging Query
	Lisp Machines: Not Everybody Likes To Program In Lisp
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Date: Friday, 23 October 1981  00:04-EDT
From: Goldberg (Robert N. Goldberg)
Re:   MC68000 paging

Someone who works for a company that produces specialized computer
systems has been telling me that they decided to build their next
system around the Z8000 rather than the MC68000 because they had
serious doubts about being able to do paging on the MC68000.  They
claim that there is a design problem that prevents instruction
resumption after a page fault.  I understand that Apollo solves the
problem by using 2 68000 chips.

Having briefly studied the instruction set and architecture of the two
CPU's, I see the MC68000 as superior for the application of this
company (they want a large virtual address space that can be accessed
from a high level language, and speed is important), and it seems to
me that getting stuck with the funny segment addressing of the Z8000
will cause problems.

1) Is there a real problem implementing virtual demand paging on the 
   MC68000?

2) Can anyone tell me some of the problems one faces when generating
   code from a compiler (e.g. C) for a segmented memory machine such
   as the Z8000?  I know that you have to do array subscripting 
   carefully, but what are some of the more insidious subtle problems
   that come up?

				Bob Goldberg

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Date: 27 Oct 1981 15:14:19-PST
From: decvax!pur-ee!purdue!cak at Berkeley
Re: Lisp Machines

I may be called a heretic for this, but here goes. The Lisp Machine
sounds very nice...I was really excited when I first saw the
announcement.  But,....
	WHAT IF YOU DON'T WANT TO PROGRAM IN LISP?
I personally am not crazy about Lisp. It is good for some things, but
for most of my hacking, I prefer C (I fight with emacs because I have
to do my extensions in MLisp. I understand why, but I don't have to
like it.)

chris

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End of WorkS Digest
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