[LAD] denormal handling

Steve Harris steve at plugin.org.uk
Fri Sep 28 09:22:17 UTC 2007

On 28 Sep 2007, at 07:51, Georg Holzmann wrote:

> Hallo!
>> our experience with ardour has been that DC bias is measurably more
>> effective at reducing CPU load than DAZ, FTZ or both combined. DAZ  
>> and
>> FTZ do both help significantly, however.
> One more question: is it not necessary to deactivate DAZ, FTZ again  
> after the application (or operation) ?
> Or is this done automatically ?
> (because I cannot see it e.g. in your ardour code)

The kernel is responsible for setting it back when it switches away  
from your process, otherwise it would be a disaster for other processes.

> Because e.g. in this document: http://developer.apple.com/ 
> documentation/Performance/Conceptual/Accelerate_sse_migration/ 
> migration_sse_translation/chapter_4_section_2.html#//apple_ref/doc/ 
> uid/TP40002729-CH248-279676
> they set it back afterwards.

Probably because they wanted to demonstrate how to turn it back on  
for later bits of code within your process that might want denormals.

- Steve

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