Date: Mon, 6 Nov 1995 10:34:37 -0600 (CST) From: Joe Diehl <joed@engg.ksu.edu> To: Jerry.Kendall@vmicls.com, hackers@freebsd.org Subject: Re: Pentium BUG Message-ID: <199511061634.KAA23017@bilbo.me.ksu.edu> In-Reply-To: <9511061410.AA16785.gonzo@vmicls.com> from "Jerry Kendall" at Nov 6, 95 09:10:22 am
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As Jerry Kendall wrote:
>
> A while ago, I read somewhere, a little test procedure that I could do
> to test and see if my Pentium had this 'well-known' bug.
>
> Does anyone know what this procedure is ???
>
> Jerry
>
Here's a small little program to test for the bug:
#include <stdio.h>
int main()
{
double x,y,z;
x = 4195835.0;
y = 3145727.0;
z = x - (x / y) * y;
printf("%f\n",z);
return 0;
}
As you can see, by simply algebra, z should always == 0; however, on
a Pentium with the FDIV bug, you can get odd answers with certain
numbers. In this case, the answer will be 256 if you have the bug,
and 0 if you don't...
Here is the sig of the guy who either wrote the code or posted the code
without any credit given to the author...
___
|0 0| Thanks,
| ^ | Duck
(\_/) Wm. David "Duck" McDonald, Anderson SC USA
,______| | and.factm.tr@ocf.compuserve.com
\______/ TOP-DUCK@genie.geis.com
Enjoy... :-)
---
Joe Diehl <joed@engg.ksu.edu>
Engineering Computing Center
Kansas State University
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