DisableMath()
-------------

Date of Release: 3/20/95

A function to disable Clipper's usage of the math coprocessor for
Clipper 5.2, 5.01, 5.0, and Summer '87.  The following files,
DISMATH.OBJ and DISMATH.ASM, have been placed in the public domain by
Greg Martin of Horizon Real-Time Systems.  You may use, modify and
distribute these files as you see fit provided the comments in
DISMATH.ASM concerning original authorship are not modified.

The purpose of the DisableMath() function is to disable Clipper's
usage of the math coprocessor when the program detects a faulty
Pentium chip thus allowing the program to continue execution without
the danger of an invalid computation being performed.  It will also
disable Clipper's usage of any math coprocessor, not just the
Pentium's, although I can think of no potential benefit for disabling
the use of a perfectly good math coprocessor.

To use the DisableMath() function simply do a well-known computational
test for a faulty Pentium and if the program determines the
computation has erred then call DisableMath().  The following example
should suffice:

   * Near beginning of program...
   IF 4195835 - ((4195835 / 3145727) * 3145727) != 0
      * Faulty Pentium found so disable math coprocessor usage
      DisableMath()
   ENDIF

DISMATH.OBJ can be linked into your executable like any other C/ASM
file -- simply add it to your linker command line or link file.  If
you are using Blinker to create real-mode applications, it can be
dynamically overlaid.  It is also compatible with protected-mode
linkers such as ExoSpace, Blinker, and Causeway.

As stated above, this function will work with versions of Clipper from
Summer '87 to Clipper 5.2 (this was one section of Clipper that didn't
change for many years), but it won't work with Clipper 5.3 or above
because Clipper 5.3 began using a different math library.

Please note that this function DOES NOT disable the math coprocessor
itself, but only Clipper's usage of it.  It does this by simply
resetting a flag deep inside the bowels of Clipper which causes
Clipper to use its own internal math library.

Also note that some third party libraries might do their own floating
point math bypassing Clipper's math library.  In that case those third
party routines might be affected by the Pentium bug.  Also note that
if you have written your own C code and are linking in Microsoft's
LLIBCE.LIB library (instead of the recommended LLIBCA.LIB) then your
Clipper code will still use the math coprocessor and be susceptible to
the Pentium bug.

You can use the enclosed TESTMATH.PRG sample code to verify the
proper functioning of the DisableMath() function.

Finally, the author grants no warranties, express or implied, by
statute or otherwise, regarding the fitness of this code for any
purpose and in no event shall be liable for any special,
consequential, or other damages.  Use at your own risk!  After all
this is public domain software and if $1000 commercial software comes
with such disclosures then surely this code qualifies too.

If you have any comments, please send them to my CompuServe address
below.

Greg Martin
Horizon Real-Time Systems, Inc.
CompuServe ID 73707,3450