Math Co-Processor Problems

tporter · ‎2003-06-13

Posted on June 13, 2003 at 14:43

tporter · ‎2003-06-12

Posted on June 12, 2003 at 17:29

All,

We have been running our software for about two years without problems on an Intel 486 processor. The motherboard we were using was discontinued and hence we have moved to a board based on the STPC Atlas processor. We are now getting errors performing floating point number comparisons, specifically if((float)Number > (float)define) where this test is giving back an occasional false positive

~(1/250000). I have confirmed that our code is using the floating point processor and not an emulator. I was wondering if anyone else has come across this problem and if they know of any solutions. The only solution we have come up with so far is to only use the less than operator, we have not seen it occur in this case.

We have performed several experiments using double to double comparisons, double to float, float to double etc.... We always run into a false positive condition eventually using the greater than operator.

Thanks,

Tom

thierry239955_st · ‎2003-06-13

Posted on June 13, 2003 at 14:43

Tom,

The core which have been integrated into STPC products is a strict copy of the Cyrix 486. It is also true for the FPU part.

Maybe you could check if you find informations about such problem on the Cyrix CPU.

Farfalla