Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!bpa!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.arch
Subject: Re: 80386 vs. 68030
Message-ID: <5375@cbmvax.UUCP>
Date: 30 Nov 88 17:30:06 GMT
References: <18266@shemp.CS.UCLA.EDU>
Organization: Commodore Technology, West Chester, PA
Lines: 38

in article <18266@shemp.CS.UCLA.EDU>, kirkaas@oahu.cs.ucla.edu (paul kirkaas) says:
> Summary: Which is better?

> So, as regards the 80386/68030 -- Which is better? Which is faster?
> Why?

Going all out, I'd expect a 68020 to be slower than an 80386 system, a
68030 to be faster.  The '030 gets a nice boost from internal instruction
and data caches and internal split I and D buses.  To go full speed, though,
an '030 will require faster memory than an 80386 running at the same clock
speed, since the '386 with it's pipelining mechanism allows full speed 
operation most of the time with slower memory.  Also, 33MHz versions of the
'030 are shipping, while the fastest available '386 is the 25MHz part.

> I'm really thinking about the NeXT vs. an 80386 based Unix machine.

That's an entirely another question.  Market competition in the PClone
area has resulted in a whole slew of really good '386 systems, with
large external static caches and other performance enhancements.  The NeXT
machine, according to all the stuff I've read at least, is only a moderate
performance 25MHz 68030 system.  For instance, the '030 in the NeXT system
requires 9 clocks to prefetch a cache line of 4 longwords; the 68030 is
capable of doing that in 5 clocks given the proper memory system.  On the
other hand, the 68030 memory management is supposedly a better match to
UNIX than that of the 80386.  

An intersting test case of this very question is coming up.  Sun is 
supposed to be about ready with a series of '030 based workstations, I
guess pretty much an upgrade of the Sun 3 series.  Comparing the UNIX
performance of one of these to the Sun 386i should be about as equal a
test as you can devise.

> Paul Kirkaas
> kirkaas@cs.ucla.edu
-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession