Path: utzoo!utgpu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!ists!yunexus!geac!maccs!antel!mike
From: mike@antel.uucp (Michael Borza)
Newsgroups: comp.unix.i386
Subject: Re: What is "__fltused" symbol?
Message-ID: <1990Feb24.230506.14711@antel.uucp>
Date: 24 Feb 90 23:05:06 GMT
References: <204@ncrday.Dayton.NCR.COM> <25da2b6b:900.1comp.unix.i386;1@vpnet.UUCP> <1990Feb21.192534.22925@eci386.uucp> <39129@ism780c.isc.com>
Reply-To: mike@antel.uucp (Michael Borza)
Organization: Antel Optronics Inc., Burlington, Ontario, Canada
Lines: 31

In article <39129@ism780c.isc.com> dougl@madison.ism.isc.com (Douglas J Leavitt) writes:
> [an interesting story about what __fltused was for...]

As an aside, it appears that a symbol named _fltused was also used in the
kernel of the 1.0.6 release which was set at boot time, based on the
configuration information in CMOS RAM.  This symbol had at least three
legal values, as I recall, indicating the presence of either a '287,
'387, or no coprocessor.  (I believe kernel support for the Weitek
chip was handled differently.)  After piecing together a 386 system
to run 386/ix on, I ported a number of integrated circuit simulation
tools to my speedy new platform.  Just for kicks, I went back to do
a comparison to my home machine, a 286 with 287 running Microport SV/AT
at the time.  Makes and edits were blindingly fast, but my 286/287
combination was keeping up handily with the floating-point intensive
simulation software.  After a couple of days on the phone with HCR,
my software vendor, we found out about _fltused, which we could inspect
and change with crash.  FP performance came up to expectations.  It
turns out that an early version of a Phoenix BIOS was to blame, which
sometimes found the 387 at boot time, sometimes not  (more times
not, as it turned out).  A quick switch to an AMI BIOS solved that
problem.

I've never gone back to see whether _fltused is used in the 2.0.x
kernel.

mike borza.
-- 
Michael Borza              Antel Optronics Inc.
(416)335-5507              3325B Mainway, Burlington, Ont., Canada  L7M 1A6
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