Date: Fri, 18 Apr 2008 18:42:26 +0900 From: "George V. Neville-Neil" <gnn@neville-neil.com> To: "Poul-Henning Kamp" <phk@phk.freebsd.dk> Cc: freebsd-current@freebsd.org, Julian Elischer <julian@elischer.org>, Andrew Gallatin <gallatin@cs.duke.edu> Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <m2fxtjts71.wl%gnn@neville-neil.com> In-Reply-To: <51610.1208498408@critter.freebsd.dk> References: <48080276.3040203@elischer.org> <51610.1208498408@critter.freebsd.dk>
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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
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