On Sun, Feb 25, 2007 at 02:56:28PM -0500, Pierre Dubuc wrote:
> No go. A bunch of daemons failed saying stuff about "no floating" 
> available or something. On my 486, the MATH_EMULATE is absolutely 
> mandatory for running even the basic stuff.

I have a 486 running without MATH_EMULATE. I just updated it's kernel to
current:

..
cpu0 at mainbus0: (uniprocessor)
cpu0: Intel 486DX (486-class)
..
npx0 at isa0 port 0xf0-0xff
npx0: using exception 16
..

then verified it has no MATH_EMULATE:

opt_math_emulate.h:/* option `MATH_EMULATE' not defined */

and then compiled and ran the following test program:

--8<--
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char **argv)
{
        char *endp;
        double v;

        if (argc < 2) return 1;
        v = strtod(argv[1], &endp);
        printf("v = %.5f, sqrt(v) = %.5f\n", v, sqrt(v));
        return 0;
}
-->8--

I verified it used the fqsrt instruction:

0x804883e <main+18>:    lea    0xfffffffc(%ebp),%eax
0x8048841 <main+21>:    push   %eax
0x8048842 <main+22>:    mov    0xc(%ebp),%eax
0x8048845 <main+25>:    pushl  0x4(%eax)
0x8048848 <main+28>:    call   0x80484e8 <strtod@plt>
0x804884d <main+33>:    fstl   0xfffffff0(%ebp)
0x8048850 <main+36>:    fsqrt  

and then ran it:

./a.out 25.23
v = 25.23000, sqrt(v) = 5.02295


Works just fine, no crash, as expected.

Is there some BIOS setting to disable the FPU on your machine?

Martin