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From: crowl@cs.rochester.edu (Lawrence Crowl)
Newsgroups: comp.arch
Subject: Re: MISC
Message-ID: <1990Sep14.205913.2146@cs.rochester.edu>
Date: 14 Sep 90 20:59:13 GMT
References: <1990Sep14.173018.10197@batcomputer.tn.cornell.edu>
Reply-To: crowl@cs.rochester.edu (Lawrence Crowl)
Distribution: comp.arch
Organization: University of Rochester Computer Science Dept
Lines: 21

In article <1990Sep14.173018.10197@batcomputer.tn.cornell.edu>
kahn@batcomputer.tn.cornell.edu (Shahin Kahn) writes:
>The latest issue of Supercomputer Review has a little report on a company
>working a "Minimum" instruction-set computer.  What is this?  Very fast
>boolean algebra?

I do not know what that project is, but I once played with an instruction set
with two instructions: "increment" and "decrement and branch conditionally".
Moving a number from one storage location to another took a loop.  Multiplying
two numbers took three nested loops.  (Exercise for the reader: Why is
"decrement and branch if not zero" better than "decrement and branch if
zero"?)  It was entertaining, but that's about it.  I'm willing to wager that
the "Minimum" above has some measure of practical in it.  You can also have a
single instruction "subtract and branch conditionally".  It has the advantage
of not requring an opcode in the instruction, just a couple of addresses.
Which instruction set is minimal depends on whether you count number of
instructions or work per instruction.
-- 
  Lawrence Crowl		716-275-9499	University of Rochester
		      crowl@cs.rochester.edu	Computer Science Department
	  ...!{ames,rutgers}!rochester!crowl	Rochester, New York,  14627