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Date: Fri, 18 Apr 2008 18:42:26 +0900
Message-ID: <m2fxtjts71.wl%gnn@neville-neil.com>
From: "George V. Neville-Neil" <gnn@neville-neil.com>
To: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: <51610.1208498408@critter.freebsd.dk>
References: <48080276.3040203@elischer.org>
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Cc: freebsd-current@freebsd.org, Julian Elischer <julian@elischer.org>,
	Andrew Gallatin <gallatin@cs.duke.edu>
Subject: Re: TSC Timecounter and multi-core/SMP 
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At Fri, 18 Apr 2008 06:00:08 +0000,
Poul-Henning Kamp wrote:
> 
> In message <48080276.3040203@elischer.org>, Julian Elischer writes:
> >David O'Brien wrote:
> >
> >> 
> >> The TSC on K8 is not invariant - its rate of change is affected by
> >> P-state changes.
> >> 
> >> The TSC on Greyhound (Family 10h) is invariant.
> >> [but as stated above, is not synced with other cores]
> >
> >You'd think that an invariant sync'd clock (fast to read) of some
> >type would have been done by someone by now.. The software people
> >have been asking for this for the last decade at least.
> 
> Actually one of the original design documents for SAGE stressed that
> such hardware were crucially important "for any system operating
> in real time", so yes, the HW people have had adequate notices.
> 

And, I suspect you mean SAGE as in Semi-Automatic Ground Environment:

http://history.sandiego.edu/GEN/20th/sage.html

and not the System Administrator's thing :-)

I'll bring some Geritol for us both to BSDCan.

Later,
George