Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!bu-cs!mirror!necntc!ima!haddock!suitti
From: suitti@haddock.ima.isc.com (Stephen Uitti)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 8087-2
Message-ID: <11437@haddock.ima.isc.com>
Date: 16 Jan 89 17:18:11 GMT
References: <408@oucsace.cs.OHIOU.EDU>
Reply-To: suitti@haddock.ima.isc.com (Stephen Uitti)
Organization: Interactive Systems, Boston
Lines: 32

In article <408@oucsace.cs.OHIOU.EDU> thollowe@oucsace.cs.OHIOU.EDU (Tom Hollowell) writes:
>I was wondering if anybody out there could tell me what the 8087-2 
>does, and whether it is worth getting.  I do know it is a math 
>co-processor for floating point arithmetic, but does it affect
>speed?  Thanks in advnace.

	I recall the 8087-2 as the 8 MHz floating point chip for
use with the 8088 processor.  My XT clone (Leading Edge Model D) runs
at 4.77 or 7.15 MHz, and I upgraded it with an 8087-2.  There are
several models of 8087, which run at different speeds.  Don't assume
that the -* number makes any sense.  The slower chip (8087-3?) runs
at 5Mhz, and for me didn't run at 7.15 (the system crashed on first
access).
	If your application doesn't use any floating point, or doesn't
look to see if the chip is out there & uses it (Turbo C applications
can do this), you won't get any improvement.  For example, the public
version of EMPIRE (Wargame of the Century) was written in FORTran and
compiled for a non-8087 environment.  It uses sine & cosine functions
with wild abandon to generate maps.  It can take a half hour to
generate a map.  If it is recompiled for an 8087 environment, the time
for map generation is about 3 minutes on the same machine (no I
haven't done this, and I don't have the source at the moment, nor do
I even have a FORTran compile for MSDOS).  This is about a x10
improvement.  I have generally seen from x8 to x45 improvements in
speed for applications that do heavy floating point, and that are or
can be compiled for using the chip.
	Similar results are obtained on Macs with 68881s, for example
in a Mac II.
	For me, the only things that really move faster are my
benchmarks.  I don't do any spreadsheet work, but rumor has it that
Lotus 123 goes much faster with one.
	Stephen.