Date: Sun, 20 Apr 2008 22:12:31 -0700 From: Julian Elischer <julian@elischer.org> To: Daniel O'Connor <doconnor@gsoft.com.au> Cc: gnn@freebsd.org, freebsd-current@freebsd.org, Andrew Gallatin <gallatin@cs.duke.edu> Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <480C223F.2040303@elischer.org> In-Reply-To: <200804181235.29530.doconnor@gsoft.com.au> References: <m2d4oy8n30.wl%gnn@neville-neil.com> <20080418003203.GB11705@dragon.NUXI.org> <48080276.3040203@elischer.org> <200804181235.29530.doconnor@gsoft.com.au>
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Daniel O'Connor wrote: > On Fri, 18 Apr 2008, Julian Elischer wrote: >> 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. > > Probably because it's very very difficult to get right :) and they've had over 20 years to think of something. >
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