Path: utzoo!utgpu!watmath!att!rutgers!ucsd!usc!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!jato!mars!kaleb
From: kaleb@mars.jpl.nasa.gov (Kaleb Keithley)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: RISC vs CISC
Message-ID: <2192@jato.Jpl.Nasa.Gov>
Date: 16 Nov 89 21:09:25 GMT
References: <29806@iuvax.cs.indiana.edu>
Sender: news@jato.Jpl.Nasa.Gov
Reply-To: kaleb@mars.UUCP (Kaleb Keithley)
Distribution: comp.binaries.ibm.pc.d
Organization: Jet Propulsion Laboratory, Pasadena, CA.
Lines: 28

In article <29806@iuvax.cs.indiana.edu> sl179060@silver.bacs.indiana.edu (Chima Echeruo) writes:
>I have an IBM AT clone (@ 20Mhz) and sometimes it seems that it is no faster
>than an AT (@12Mhz). Most of the bottlenecks seemed to be the disk IO and
>the graphics card (8 bit EGA). I expected the 20 Mhz 286 to average 8+ MIPS and
>when I ran the MIPS (Chips & Tech) benchmark, I got a disappointing 2.5 - 3.00
>MIPS. Does that mean that the 'average' 286 instruction takes 8 cycles?

Put some extended memory in, and use a disk cache device driver, like
SMARTDRV.SYS (DOS 4.01), this will greatly improve disk performance, and
alleviate the disk bottleneck.

>Would the RISC 286 (@10 Mhz) not outperform the CISC 286 (@20)? What are the
>factors involved in the decision to make a chip RISC or CISC?

There may be more technical answers than this one, but the instruction set
is what determines RISC vs CISC.  If you had a different instruction set,
then it wouldn't be a 286 any more.  Furthermore, the 80x86 is a micro-coded
machine, and most RISC machines have a hard coded instruction set.  NEC was
rumored to be producing a V33, essentially an 8086 with hard coded logic,
rather than micro-coded logic.  I don't know if it ever came to be.  But 
it was thought that it would be blazingly fast compared to an Intel micro-
code 8086.  These rumors circulated around the time when NEC was doing
legal battle with Intel over Vx0/80x86 copyright/patent infringements, so
the death of the Vx3 family may have been because of this.
Benson, you are so mercifully devoid of the ravages of intelligence.

kaleb@mars.jpl.nasa.gov             (818)354-8771
Kaleb Keithley