[linux-audio-dev] P4 kernel patch/option against denormals

Ralf Beck musical_snake at gmx.de
Sun Sep 19 17:07:32 UTC 2004

The following proggi does the job:

#include <xmmintrin.h>

#define _MM_DENORM_ZERO_ON    0x0040

// enable flush to zero
 _mm_setcsr(_MM_FLUSH_ZERO_ON | _MM_MASK_UNDERFLOW | _mm_getcsr());

// enable denormals are zero
 _mm_setcsr(_MM_DENORM_ZERO_ON | _mm_getcsr());

Note: you will need compiler option -mfpmath=sse and -march=pentium4 
(works for both P4 and Athlon64)

After reboot, both FZ and DAZ flags are reset to zero, so you should run this 
program in your /etc/profile. But as said earlier,  works only for 
applications that use (are compiled to use) the SSE unit instead of the old 
style X86 FPU.

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