Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!uunet!dg!rec
From: rec@dg.dg.com (Robert Cousins)
Newsgroups: comp.arch
Subject: Re: specmarks
Message-ID: <225@dg.dg.com>
Date: 26 Oct 89 18:42:26 GMT
References: <327@ssp1.idca.tds.philips.nl> <4420015@hpihoah.HP.COM>
Reply-To: uunet!dg!rec (Robert Cousins)
Organization: Data General, Westboro, MA.
Lines: 42

In article <4420015@hpihoah.HP.COM> fotland@hpihoah.HP.COM (David Fotland) writes:
>This seems to clearly show the advantage of RISC over 68K type machines.  I
>think it also seems to show the disadvantage of register windows, since
>PRISM, MIPS, and PA don't have them and SPARC and 88K have them.
 
Before comparing numbers, one should make sure that compared machines are
comperable.  It is easy to see numbers based uon various CPUs and ignore the
remaining system characteristics such as RAM capacity and speed, Cache size,
OS, peripheral speed, etc.  The SPEC benchmarks are heavily tilted toward
Fortran floating point and can have a large memory useage in some cases. These
have SYSTEM performance implications which can dwarf the CPU impact.

Actually, the 88K does not have register windows.  However, the 88K numbers
which were published are not based on representative hardware and software.
You will see better SPEC numbers on 88K machines very soon now.
While I agree that Regiser Windows are not the total salvation which some
people believe them to be, the real point is the RISC does beat CISC quite 
handily.  

Lastly, by computing a "figure of merit" based upon a benchmark is quite dangerous.
The 88K, for example, is exceptionally good a certain benchmarks. So is the 80386.
If one searches for the proper combination of benchmarks, one could prove almost
anything.  In a previous life as a consultant, I was told an apocryphal story concerning
the then fastest computer on earth, the TI ASC and the TI 990 minicomputer. It appears
that DOD wouldn't buy the ASC  without a COBOL compiler due to DOD rules even though
the DOD would never run anything but FORTRAN on the machine.  As a result, the COBOL
for the 990 was fudged over onto the ASC in some form of interpreted mode (details
escape me, it's been many years).  As a result, the 990 would handily outperform
the ASC on all manner of COBOL benchmarks including the US Steel (the "standard
COBOL benchmark ofthe day").



>
>David Fotland


Robert Cousins
Dept. Mgr, Workstation Dev't.
Data General Corp.

Speaking for myself alone.