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From: lotto@wjh12.UUCP (Jerry Lotto)
Newsgroups: comp.sys.ibm.pc,comp.sources.d,comp.sys.intel
Subject: 80287 FLD ST(0) - causes my AT to hang!
Message-ID: <35@wjh12.UUCP>
Date: Fri, 21-Nov-86 11:10:56 EST
Article-I.D.: wjh12.35
Posted: Fri Nov 21 11:10:56 1986
Date-Received: Fri, 21-Nov-86 20:21:16 EST
Reply-To: lotto@wjh12.UUCP (Jerry Lotto)
Distribution: net
Organization: Harvard Univ. Chem. Dept.
Lines: 17
Xref: mnetor comp.sys.ibm.pc:181 comp.sources.d:34 comp.sys.intel:44


A recent posting in net.sources (gnuplot), compiled with Microsofts C
compiler v 4.0 causes my machine to hang up. Only a hard reset brings
it back. I traced the problem to a single machine instruction! The
problem arises in the _log10 routine.

In the debugger(s), I was able to trace the problem down to the
following. There are three items on the stack, and we hit an FLD
ST(0). This is supposed to duplicate the top item on the stack. On my
machine, it operates similarly to a HALT.  The 80287 appears to be
well before the instruction.  Stepping to it, manually setting up the
80287, etc. all give the same results. Other 80287 instructions work
just fine.

I have yet to try this on another box. I assume everything will work
out OK. Does anyone know what could be going on here? Thanks in
advance for any light that can be shed on this problem.