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From: ctk@ecsvax.UUCP (Tim Kelley)
Newsgroups: net.arch,net.lang.c,net.micro,net.micro.pc,net.micro.68k
Subject: Re: Re: Re: Need 286 "C" benchmark
Message-ID: <1338@ecsvax.UUCP>
Date: Tue, 28-May-85 07:36:02 EDT
Article-I.D.: ecsvax.1338
Posted: Tue May 28 07:36:02 1985
Date-Received: Thu, 30-May-85 04:15:58 EDT
References: <426@oakhill.UUCP> <8745@microsoft.UUCP> <583@intelca.UUCP> <433@oakhill.UUCP> <588@intelca.UUCP> <5631@utzoo.UUCP>
Reply-To: ctk@ecsvax.UUCP (Tim Kelley)
Organization: NCSU Dept. of mathematics
Lines: 19
Xref: watmath net.arch:1267 net.lang.c:5310 net.micro:10548 net.micro.pc:4065 net.micro.68k:822
Summary: 

This is yet another comment on the fairness of benchmarks using >64k
data on the *86 chips. I do this on IBM-PC/AT's every day for floating
point work. Most of my data consists of matrices of doubles. I have
coded things like dot products and daxpys in assembler, and observe
that the penealty for using the large model is very small. For problems
for which both models can be used, the large model code is about 5%
slower if written correctly. However, the real limit is the 1meg that
one can use without going to protected mode. This is often a real pain.
	I run MS-DOS (not XENIX) and don't use protected mode. Does anyone
know what the speed penalty for using protected mode is? Looks like a
lot. I am not defending Intel, having to fool around with segments is
a waste of time. However, where was a system that worked with hardware
floats for <$3000 three years ago (hint: IBM).


-- 
C.T. Kelley  decvax!mcnc!ecsvax!ctk
Dept. of Math.    N.C. State U. Box 8205
Raleigh, N.C. 27695-8205,  919-737-7895