[PD] iemlib-filters and Pentium-NaNs

Frank Barknecht barknech at ph-cip.uni-koeln.de
Fri Jul 19 11:00:11 CEST 2002

Olaf Matthes schrieb:
> Yes, with the cverb~ external.... After turning off the input signal CPU usage jumped up to 80 %
> or more (for one object!) after a second or so. This is due to the architecture of the CPU that
> switches to (slow) floating point mode. To prevent this just do the following
> if(((*(unsigned int*)&sample)&0x7f800000)==0) sample=0.0
> whereever a signal gets smaller without realy getting zeroe (like in the reverb tail of cverb~,
> freeverb~ and the like).
> Olaf
> PS: I think there is a document at htt://musicdsp.org describing more / other methods of
> undenormalisation
For those speaking german, the July-issue of "Keyboards" magazine observed
a similar thing in VST plugins etc. on Pentium IV processors. Obviously
Intel changed the handling of denormalisation in the newer processors, so
that older counter measures against denorm. fail again. 

Interesting article...

Frank Barknecht <barknecht at dradio-online.de>
           -= www.dradio.de =-
DeutschlandRadio-Online * Redaktion Köln
tel 0221 - 345 1471 * fax 0221 - 345 1480

More information about the Pd-list mailing list