Subject: Re: Calibration issues with USB disc present.
From: Lee Revell <rlrevell@joe-job.com>
To: Max Krasnyansky <maxk@qualcomm.com>
Cc: george@mvista.com, john stultz <johnstul@us.ibm.com>,
       Greg KH <greg@kroah.com>, ganzinger@mvista.com,
       lkml <linux-kernel@vger.kernel.org>
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	 <20051114184940.GA876@kroah.com> <1131998339.4668.16.camel@leatherman>
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Date: Wed, 16 Nov 2005 19:30:23 -0500
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On Wed, 2005-11-16 at 16:03 -0800, Max Krasnyansky wrote:
> I think in the short term your best bet is to globally disable SMI at
> early
> boot stage (ie before TSC calibration).
> Some people might argue that it's not the most graceful solution
> because it might
> brake some BIOS features but it's a very common trick that is used by
> RT folks
> (for example RTAI has configurable option to enable SMI workaround)
> because
> on some chipset/BIOS combinations SMIs introduce horrible latencies.
> And you
> cannot do much about that other than disabling SMI.
> I have not seen any reports of negative side effects of disabling SMI
> yet. But
> if you're worried about that you could re-enable it later when you're
> done with
> TSC calibration and stuff.
> 

Hmm, interesting, I had no idea this was possible.  Is there a generic
way to disable SMI?  It would be useful for the -rt tree as lots of low
latency audio users have problems with SMI induced underruns.

Lee

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