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From: mwm@eris (Mike (I'm in love with my car) Meyer)
Newsgroups: comp.misc,comp.arch
Subject: Re: Japanese 32-bit micro can be a 68020 or 80386
Message-ID: <10076@agate.BERKELEY.EDU>
Date: 18 May 88 03:09:34 GMT
References: <2006@sugar.UUCP>
Sender: usenet@agate.BERKELEY.EDU
Reply-To: mwm@eris.UUCP (Mike (I'm in love with my car) Meyer)
Organization: Missionaria Phonibalonica
Lines: 48

In article <2006@sugar.UUCP> karl@sugar.UUCP (Karl Lehenbauer) writes:
<(sorry, I don't have the article at hand) that has a writable control store 
<and thus can have different microprograms loaded into it to emulate the 80386,
<68020 and others, apparently as a means of getting around microcode copyright 

This isn't anything new. I've even worked on machines that had
writeable control store for the nanocode level, so you could implement
whatever you wanted for a micromachine (wanna run the 68020 microcode
on it? Sure - no problem.... :-).

<Even the immediate implications are stunning, I think.  One thing is that 
<those of us who have always wanted to diddle microcode may soon be able to, 
<tho' there won't be much software or software compatibility for those who

Check out the PDP-11/60. Or almost any VAX. Or ask DEC about the WCS
board for the micro-11 (11/03? The one sold by Heath for a while).
I've even got a computer architecture text that discusses putting a
butterfly FFT into the WCS on the 11/60. You might even ask BBN about
the C/70.

<Imagine a version of the microprogrammable chip in which the operating system 
<could context switch among trusted sets of microprograms.  Weird.

Burroughs has been doing that for years. You get to design the target
machine when you design a compiler. Doing that leads to oddities like
instruction sets with a push but no pop (you push args, then subtract
from the stack pointer to unpop them all).

<Imagine a virtual personal computer which, on exactly the same hardware, 
<could be a DOS-compatible 80386 workstation or a 68020 workstation, with 
<microcode and software being the only differences.  How about a
<Forth machine?  A Vax?

At what cost? You'll notice that Burroughs has been loosing ground to
DEC, and DEC has been loosing ground to various RISC-machine
companies. And the magic machine with the WCS for both micro and nano
code is no longer sold at all.

For instance, can anyone provide performance figures for the virtual
microprocesser in 68020 mode? Assuming I did the right magic on a
daughter board, could I plug it into a Sun 3/280 and get the same
performance as I do from the 68020?

	<mike
--
The weather is here, I wish you were beautiful.		Mike Meyer
My thoughts aren't too clear, but don't run away.	mwm@berkeley.edu
My girlfriend's a bore, my job is too dutiful.		ucbvax!mwm
Hell nobody's perfect, would you like to play?		mwm@ucbjade.BITNET