Subject: Re: kernel options MATH_EMULATE (was: Re: mk.conf and "I387_LIBM")
To: Richard Rauch <>
From: Manuel Bouyer <>
List: port-i386
Date: 10/23/2000 10:51:41
On Sun, Oct 22, 2000 at 09:03:06PM -0500, Richard Rauch wrote:
> My understanding is that MATH_EMULATE is used in the kernel config solely
> to determine whether the kernel will use FP instructions (and hence
> registers).  By turning on MATH_EMULATE, you cause kernel FP operations to
> be emulated, so the kernel doesn't need to fret with the FP registers,
> and/or if the kernel has the FP registers saved, it may then freely use
> them as temporaries for data-copy loops.

No. This enable the kernel floating point emulator, which is used when an
FPU instruction is encountered on a FPU-less CPU. On a CPU with a FPU,
MATH_EMULATE doesn't change anything.

The kernel doesn't use any FP instruction.

Manuel Bouyer, LIP6, Universite Paris VI.