Subject: Re: [linux-audio-dev] P4 kernel patch/option against denormals
From: Ralf Beck (musical_snake_AT_gmx.de)
Date: Sun Sep 19 2004 - 14:38:07 EEST
The problem is apparent on all P4s.
Also the DAZ (Denormals are Zero) and FTZ (Flush to zero) flags are available
on any processor which has a SSE2 unit implemented, e.g. all P$ and AMD64s.
Saying that, they are effective only when using the SSE(2) unit for
calculations.
You con try to use SSE by adding the CC options -mfpmath=sse and
-march=pentium4 when compiling. Some operations (like log, exp sin ) will
still be caluculated in ht e old X86 Fpu, though.
And of course write a small proggi that sets the FTZ and DAZ flags.
An easy way for implementors to avoid denormals is to add and subtract a small
value big enough to clear out the mantissa and thus make denormals zeros.
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