From owner-freebsd-current Mon Nov 23 17:45:41 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id RAA17068 for freebsd-current-outgoing; Mon, 23 Nov 1998 17:45:41 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from wall.polstra.com (rtrwan160.accessone.com [206.213.115.74]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id RAA17063 for ; Mon, 23 Nov 1998 17:45:38 -0800 (PST) (envelope-from jdp@polstra.com) Received: from vashon.polstra.com (vashon.polstra.com [206.213.73.13]) by wall.polstra.com (8.9.1/8.9.1) with ESMTP id RAA20955; Mon, 23 Nov 1998 17:41:43 -0800 (PST) (envelope-from jdp@polstra.com) Received: (from jdp@localhost) by vashon.polstra.com (8.9.1/8.9.1) id RAA01311; Mon, 23 Nov 1998 17:41:43 -0800 (PST) (envelope-from jdp@polstra.com) Message-ID: X-Mailer: XFMail 1.3 [p0] on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <44808.911870229@zippy.cdrom.com> Date: Mon, 23 Nov 1998 17:41:43 -0800 (PST) Organization: Polstra & Co., Inc. From: John Polstra To: "Jordan K. Hubbard" Subject: Re: Random craches under heavy(?) disk activity Cc: current@FreeBSD.ORG, rom_glsa@ein-hashofet.co.il, Poul-Henning Kamp Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 24-Nov-98 Jordan K. Hubbard wrote: >> I would actually argue that the longer the box has been overclocked >> the warmer the cpu runs. > > I've also had OC'd boxes start failing. A trusty PPro 233 of mine ran > OC'd for almost 2 years before finally starting to exhibit occasional > flakiness. I now run it at 200 and it's happy again. I wouldn't trust it even back at 200. Overclocking causes overheating, and it's not uniform overheating. Every chip has hot spots which get much hotter than others. Research has clearly shown that such localized overheating damages the chips, makes them less reliable, and shortens their lifetimes. I used to do a lot of consulting work for a company that built equipment for diagnosing problems in digital circuit boards. The goal was to find the bad chip on the board, and the essence of the process was to somehow inject test patterns that would stimulate the inputs of individual chips in controlled ways, and then see whether their outputs matched expectations. We investigated a technique called overdriving. The idea was that you used high-current drivers to just blast the test patterns into the chips' inputs, very briefly overwhelming the outputs of the chips that were driving those inputs. The hope was that we could keep the duration of the overdriving brief enough so that the other chips wouldn't be damaged. We abandoned it eventually. Even the shortest useful periods of overdriving were enough to reduce the lifetimes of the chips being overdriven. I believe that similar damage most likely occurs when you overclock a CPU. It doesn't mean a thing that the package feels cool. There can still be tiny spots on the chip that are badly overheated. John --- John Polstra jdp@polstra.com John D. Polstra & Co., Inc. Seattle, Washington USA "Nobody ever went broke underestimating the taste of the American public." -- H. L. Mencken To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message