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From: john@bby-bc.UUCP (john)
Newsgroups: comp.sys.intel,comp.sys.ibm.pc
Subject: 80827 affects speed of 80286? (July Byte)
Message-ID: <131@bby-bc.UUCP>
Date: Fri, 3-Jul-87 23:23:05 EDT
Article-I.D.: bby-bc.131
Posted: Fri Jul  3 23:23:05 1987
Date-Received: Sat, 4-Jul-87 19:41:37 EDT
Organization: Burnaby, British Columbia, Canada
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Xref: mnetor comp.sys.intel:289 comp.sys.ibm.pc:5304


In the July issue of Byte they benchmark the 68020 and 80386
using (among others) the dhrystone benchmark.  They also give
figures for the 80286 as a comparison.  The figure for an 80286
with an 80287 is 13% faster than a 80286 alone but as I recall
the Dhrystone benchmark doesn't do any floating point so this
would indicate that the 80287 somehow speeds up the 80286 non
float instructions somehow - is that really the case or are the
results bogus?  The actual numbers given are:

IBM PC-AT (8mhz)	1567.9
IBM PC-AT (8mhz)+80287	1748.9

Also elsewhere in the issue (the BIX stuff) someone claims the
following results for the 386 (Dhrystones again):


				protected mode		nonprotected

Compaq 386 16mhz		5850			2380
386 Hummingboard 16mhz		6730			2777
386 Hummingboard 20mhz		8650			3571
Intel 386/20			6700			----

The nonprotected mode was using Microsoft C in large model.
The protected mode used Metaware 386 High C in small (4 gigabyte segs)
model.

8650 is pretty impressive.

Anyone have a capsule description as to why protected mode is so
much faster?

john