From owner-freebsd-current@FreeBSD.ORG Thu Apr 10 22:38:49 2008 Return-Path: Delivered-To: current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 374931065671 for ; Thu, 10 Apr 2008 22:38:49 +0000 (UTC) (envelope-from gary@velocity-servers.net) Received: from longhorn.velocity-servers.net (longhorn.velocity-servers.net [65.99.246.30]) by mx1.freebsd.org (Postfix) with ESMTP id 17C278FC24 for ; Thu, 10 Apr 2008 22:38:48 +0000 (UTC) (envelope-from gary@velocity-servers.net) Received: from pool-70-106-53-131.hag.east.verizon.net ([70.106.53.131] helo=dragoon.velocity-servers.net) by longhorn.velocity-servers.net with esmtpa (Exim 4.69 (FreeBSD)) (envelope-from ) id 1Jk593-000NMv-VK; Thu, 10 Apr 2008 17:21:26 -0500 X-Mailer: QUALCOMM Windows Eudora Version 7.1.0.9 Date: Thu, 10 Apr 2008 18:21:19 -0400 To: "Poul-Henning Kamp" From: Gary Stanley In-Reply-To: <1248.1207863941@critter.freebsd.dk> References: <1248.1207863941@critter.freebsd.dk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - longhorn.velocity-servers.net X-AntiAbuse: Original Domain - freebsd.org X-AntiAbuse: Originator/Caller UID/GID - [26 6] / [26 6] X-AntiAbuse: Sender Address Domain - velocity-servers.net Message-Id: <20080410223849.17C278FC24@mx1.freebsd.org> X-Mailman-Approved-At: Thu, 10 Apr 2008 22:51:14 +0000 Cc: current@FreeBSD.org Subject: Re: TSC Timecounter and multi-core/SMP X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Apr 2008 22:38:49 -0000 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.