Re: High pitched noise from laptop: processor.c in linux 2.6

[Lee Revell]

On Sat, 2004-10-16 at 22:21, Alan Cox wrote:
> On Sul, 2004-10-17 at 02:24, Lee Revell wrote:
> > > And heavily reduced accuracy on a lot of laptops where 1000Hz
> > > is enough to make the clock slide every time the battery state is
> > > queried or an SMM event triggers.
> > Wouldn't such a laptop be horribly broken?  1ms is a LONG time to
> > disable interrupts.  That's millions of CPU cycles...
> 
> Yes, and most laptops have this problem. They use SMM traps to talk to
> the battery including huge delay loops and during those SMM traps no
> interrupt code runs.
> 

Ugh!  I was under the impression that mostly older machines had this
problem and it was a minority of laptops.  I could not find a lot of 
info on SMM  - several of the links I found were DDJ "Undocumented
Corner" articles.

Anyway this explains probably half the weird bug reports on the linux
audio user list.

Lee

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