Date: Thu, 10 Apr 2008 18:21:19 -0400 From: Gary Stanley <gary@velocity-servers.net> To: "Poul-Henning Kamp" <phk@phk.freebsd.dk> Cc: current@FreeBSD.org Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <20080410223849.17C278FC24@mx1.freebsd.org> In-Reply-To: <1248.1207863941@critter.freebsd.dk> References: <Your message of "Thu, 10 Apr 2008 13:52:28 MST." <47FE7E0C.4070801@FreeBSD.org> <1248.1207863941@critter.freebsd.dk>
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At 05:45 PM 4/10/2008, Poul-Henning Kamp wrote: >In message <47FE7E0C.4070801@FreeBSD.org>, Maxim Sobolev writes: > >Kris Kennaway wrote: > >> gnn@freebsd.org wrote: > >>> Howdy, > >>> > >>> Is the TSC timecounter synchronized across multiple cores and/or > >>> processors? A quick search seems to indicate it's not but I'd like to > >>> find a definitive reference on the TSC. > >> > >> Modern Intel systems tend to be synchronized, in my experience. > > > >I really doubt they are. As far as I know newest milti-core chips can > >modulate frequency of even suspend individual cores independently of > >each other, which would make such synchronization difficult to maintain > >if the power management is on. > >P4 (and I think most newer chips) have a TSC that runs independent >of the cpu clock frequency, and supposedly, always at constant rate. > Are you talking about the RDTSCP? I think its only on newer opterons and phenoms.
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