Xref: utzoo comp.sys.m68k:1752 comp.arch:17099
Path: utzoo!attcan!uunet!dino!sharkey!msuinfo!news
From: fox@VIXEN.NSCL.MSU.EDU
Newsgroups: comp.sys.m68k,comp.arch
Subject: Re: Moto's data predicts 68040 performance well below 20 MIPS
Message-ID: <1990Jul13.163849.4282@msuinfo.cl.msu.edu>
Date: 13 Jul 90 17:37:00 GMT
Sender: news@msuinfo.cl.msu.edu
Organization: National Superconducting Cyclotron Lab
Lines: 39

In article <40088@mips.mips.COM>, mark@mips.COM (Mark G. Johnson) writes...

>The June 1990 issue of _IEEE_Micro_ contains an article about the
>Morotola 68040, written by some of its designers.  The article agrees
>with some of the advertising copy, saying "The sustained
>performance level is 20 VAX-equivalent MIPS and 3 Mflops at a clock
>speed of 25 MHz."  (1st paragraph, 4th sentence).
> 
>Later in the article, Figure 2 is particularly interesting; its caption reads
>   "Processor performance relative to the 68020   versus   cache size
>    (where the 68020 equals 1)."
> 
>For the cache sizes actually used in the 68040 (4Kbytes), the
>performance plotted in Figure 2 [68040 normalized to 68020] is in
>the range 3.6X to 4.3X, depending upon the workload.  Most of the
>benchmarks shown are at 4.1X.
> 
>So, the data and the claim that 68040==20VAXmips  implies that the earlier
>68020 has a "sustained performance level of 4.9 VAX-equivalent MIPS"
>(4.9 = 20/4.1).  Does anybody seriously believe this?
> 
>About the most impartial data I could find was for the Hewlett Packard
>HP9000 model 370 machine.  This uses a 68030 (not 68020) at 33 MHz (not
>25 MHz) and achieves a geometric mean of 3.9 SPECmarks [ref. SPEC
>newsletter v1#1].  It seems reasonable to suspect the 68020 is no
>better than the 030 in performance {else who'd want the 030?}, so we
>conclude that the 020's performance is, at most, 3.9 VAX-equivalent
>MIPS.  This makes the 68040 a 16 VAXmips machine (at most), not 20 VAXmips
>as advertised.

For much of the stuff we run, 16Mhz 68020 + 68881 runs at about .8 VAX
mips. (Scientific technical applications). So it seems to me that
25Mhz could be no faster than 25/16 * .8 = 1.25 VAX mips.

Ron Fox                     | FOX@MSUNSCL.BITNET      | Where the name 
NSCL                        | FOX@CYCVAX.NSCL.MSU.EDU | goes on before
Michigan State University   | MSUHEP::CYCVAX::FOX     | the quality
East Lansing, MI 48824-1321 |                         | goes in.
USA