Path: utzoo!yunexus!davecb
From: davecb@yunexus.UUCP (David Collier-Brown)
Newsgroups: comp.arch
Subject: Re: Compiling - RISC vs. CISC
Keywords: CISC, vCISC, compiler
Message-ID: <2613@yunexus.UUCP>
Date: 10 Jul 89 02:27:25 GMT
Article-I.D.: yunexus.2613
References: <13976@lanl.gov>
Reply-To: davecb@yunexus.UUCP (David Collier-Brown)
Organization: York U. Computing Services
Lines: 44

In article <13976@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>Every once in a while, someone in this newsgroup makes the claim
>that RISC trades off hardware complexity for compiler complexity.
>This is simply _NOT_ true.  It is always _easier_ to write a compiler
>for a RISC machine than for a CISC machine.
[well-reasoned arguement for a Vax]

  If one is to consider CISC machines, there are two things to
remember:
	1) they come in families
	2) the popular ones aren't always the ones you want to consider.

  The IBM /360 and VAXen are good examples of a particular era.  That does
not make them the only CISC machines.  
  The Honeywell (now Bull) DPS-8 is a conscious attempt at a
very-complex-instruction set computer, based on the basic architecture
of the era of IBM 7090s and DEC-10s.  Given a compiler (say, FORTRAN
IV) for the basic machine language, one can add all the constructs for
PL/1 and (you should pardon the expression) COBOL to your language in
about two man-days: Honeybun put the primitives into the EISbox
(Extended Instruction Set).

  One can even generate good code for them (;-)), because they're
either
	regular, or
	only exist in one variant.

  The machine is still in production, is still very CISC, and actually
runs rather well.  They really did "narrow the semantic gap between
the machine language and the language understood by the compiler",
which was the reason d'etre of the vCISC machines.

 Mind you, I can't recommend the underlying order code (the stuff that
preceded the EISbox) to my worst enemy.  The machine is a sorta wart
with an elegant bag on the side.

  And Waterloo even has a very standard/rather good C compiler for it.

	       --dave (I once worked on Honeybuns) c-b
-- 
David Collier-Brown,  | davecb@yunexus, ...!yunexus!davecb or
72 Abitibi Ave.,      | {toronto area...}lethe!dave 
Willowdale, Ontario,  | Joyce C-B:
CANADA. 223-8968      |    He's so smart he's dumb.