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Date: Tue, 12 Sep 2006 16:56:18 -0600 (MDT)
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To: John.Giacomoni@colorado.edu
From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: Detect Bus Speed?
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In message: <2D3EAACB-BB70-45B1-A018-EBCF7126F7E9@colorado.edu>
            John Giacomoni <John.Giacomoni@colorado.edu> writes:
: Is there a way to determine the current bus speed a PCI-X slot is  
: running at?

Not easily.  The host's BIOS controls that, and some power management
strategies clock down the bus from time to time to save power...

If you have something that's bus speed dependent, it might be better
to use a strategy that instead responds to events that you can
control, like DMA completion and the like and adapt in real time.

Warner