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From: rwood@vajra.uucp (Richard Wood)
Newsgroups: comp.sys.dec
Subject: Re: DECstation 3100 - is it fast?
Message-ID: <473@granite.dec.com>
Date: 29 Apr 89 00:18:14 GMT
References: <2056@gluteus.ai.mit.edu>
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Cracraft@wheaties.ai.mit.edu (Stuart Cracraft) writes:
> 
> After benchmarking the new 3100 with a C dhrystone program
> (25,000 dhrystones per second), I felt it would probably
> do pretty well on an application, since a VAX 8810 scored
> 8,333 dhrystones per second with the same C program.
> 
> Imagine my surprise when the application ran only marginally
> faster on the 3100 (unloaded) than on the 8810!
> 
> Do you think (dare say) these machines are optimized for
> the typical benchmarks?
> 
> 	Stuart

If you compare that Dhrystone number to "MIPS" as defined by some of our
more aggressive competitors, you'd probably discover that our box is
rated at over 16 "Dhrystone MIPS".  This isn't a term Digital likes to
use, because it implies more than we (or anyone) can deliver.

To judge a machine by a toy program that will fit in the cache of about
every machine that has one is silly.  It also ignores that fact that the
overwhelming number of applications are not wholly compute intensive -
they usually have a good mix of compute and I/O.

DIGITAL DOES NOT DESIGN MACHINES TO RUN WELL IN BENCHMARKS.

If we did, we'd also be the kind of company that would claim as our
performance numbers some point way off the curve.  We do things
conservatively, as befits a corporation that other companies depend on
to state reasonable claims.

(Note that the VAX 8810 is rated by DEC at 7 VUPS (where VUP is a
conservative estimate of the factor greater than a VAX 11/780 running
the same operating system and compilers), while the DECstation 3100 is
rated at about 12 VUPS.  It is quite within reason that the DS3100
would only be "marginally" faster - there are some things that the
large VAXes are very good at, while the MIPS processor might not do
quite as well.


Tell us more about the application, and perhaps the mystery will
evaporate.

-- ----------------------------------------------------------------------------
Does it need saying that I'm not speaking as an official representative of DEC?
===============================================================================
Richard Wood  !  U. S. Worksystems, Palo Alto  !  Digital Equipment Corporation