Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!batcomputer!rpi!crdgw1!steinmetz!sungod!davidsen
From: davidsen@sungod.steinmetz (William Davidsen)
Newsgroups: comp.arch
Subject: Re: 68020 vs. 68030 speed (was Re: 80486 vs. 68040 code size)
Message-ID: <13804@steinmetz.ge.com>
Date: 15 May 89 14:55:05 GMT
References: <922@aber-cs.UUCP> <8081@killer.Dallas.TX.US> <700@tukki.jyu.fi> <4175@ficc.uu.net>
Sender: news@steinmetz.ge.com
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
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Organization: General Electric CRD, Schenectady, NY
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In article <4175@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes:
| One thing you have to keep in mind in the 80386 versus 68030 debate is
| that, yes, there are fewer 68030 systems out there then 80386 boxes...
| but the vast majority of the 80386 systems are crippled by the poor
| performance of the AT bus. I have been benchmarking a 25 MHz 386 against
| our 16 Mhz 80286es on multibus. The speed advantage of the 80386 is
| almost entirely lost in the low performance of the bus. In fact many
| of our development tools run faster on the 286 or on a 386 in 286 mode
| on the multibus.

  You don't seem to mention what o/s you're using to determine this.
Given any particular architecture, using a 16 bit o/s like MS-DOS, there
will be very little performance diference between the 286 and 386.
However, if the 386 code uses the full instruction set, it should run
much faster than a 286 at the same speed, running the best 16 bit
version of the same program. Of course there can be programs written to
always use 16 bit data, so this is not an absolute.

  When I got my first 386 UNIX system I ran some programs compiled for
286 on the 386, under the 386 o/s. With no other change than
recompilation most programs ran about 2:1 faster. These programs were
mainly data compression programs (compress, zoo), and some text
processing tools.

  Perhaps you could clarify conditions you are observing.
	bill davidsen		(davidsen@crdos1.crd.GE.COM)
  {uunet | philabs}!crdgw1!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me