From owner-freebsd-hackers@FreeBSD.ORG Thu Dec 14 20:47:10 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id F391416A509 for ; Thu, 14 Dec 2006 20:47:09 +0000 (UTC) (envelope-from mldodson@houston.rr.com) Received: from ms-smtp-04.texas.rr.com (ms-smtp-04.texas.rr.com [24.93.47.43]) by mx1.FreeBSD.org (Postfix) with ESMTP id AB88143DB5 for ; Thu, 14 Dec 2006 20:36:19 +0000 (GMT) (envelope-from mldodson@houston.rr.com) Received: from localhost.houston.rr.com (cpe-24-167-77-130.houston.res.rr.com [24.167.77.130]) by ms-smtp-04.texas.rr.com (8.13.6/8.13.6) with ESMTP id kBEKbTRQ026226 for ; Thu, 14 Dec 2006 14:37:29 -0600 (CST) Received: from localhost (localhost [[UNIX: localhost]]) by localhost.houston.rr.com (8.13.8/8.13.6/Submit) id kBEKbSHp069928 for freebsd-hackers@freebsd.org; Thu, 14 Dec 2006 14:37:28 -0600 (CST) (envelope-from mldodson@houston.rr.com) X-Authentication-Warning: localhost.houston.rr.com: bdodson set sender to mldodson@houston.rr.com using -f From: "M. L. Dodson" To: freebsd-hackers@freebsd.org Date: Thu, 14 Dec 2006 14:37:28 -0600 User-Agent: KMail/1.9.4 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200612141437.28724.mldodson@houston.rr.com> X-Virus-Scanned: Symantec AntiVirus Scan Engine X-Mailman-Approved-At: Thu, 14 Dec 2006 23:06:33 +0000 Subject: "Syncing cpus" on a multi-cpu, dual core system X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: mldodson@houston.rr.com List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 14 Dec 2006 20:47:10 -0000 On a computational chemistry list I subscribe to there is a current thread about multi-cpu systems needing to have the cpu frequencies synced (this is in a Linux context). This is evidently not just having the cpus running at nominally the same frequency but something else in addition. A posting in the thread said variations less than 0.1% were not problematic. However, the poster said it was an issue in a dual cpu, dual core system he had set up. My questions are: 1. Is this real or an urban legend? 2. If real, is this a Linuxism or is FreeBSD affected as well? 3. How do you "sync" the cpus, if it is needed? 4. anything else some one wants to expound on along this line. Bud Dodson -- M. L. Dodson Email: mldodson-at-houston-dot-rr-dot-com Phone: eight_three_two-56_three-386_one