From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 9 Jun 2001 03:56:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 9 Jun 2001 03:56:24 -0400 Received: from neon-gw.transmeta.com ([209.10.217.66]:13320 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id convert rfc822-to-8bit; Sat, 9 Jun 2001 03:56:12 -0400 To: linux-kernel@vger.kernel.org From: "H. Peter Anvin" Subject: Re: temperature standard - global config option? Date: 9 Jun 2001 00:55:42 -0700 Organization: Transmeta Corporation, Santa Clara CA Message-ID: <9fskpu$nh6$1@cesium.transmeta.com> In-Reply-To: <200106082116.f58LGd2497562@saturn.cs.uml.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Disclaimer: Not speaking for Transmeta in any way, shape, or form. Copyright: Copyright 2001 H. Peter Anvin - All Rights Reserved Content-Transfer-Encoding: 8BIT X-MIME-Autoconverted: from 8bit to quoted-printable by deepthought.transmeta.com id AAA27744 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Followup to: By author: Chris Boot In newsgroup: linux.dev.kernel > > Well then, tell all the teachers in this world that they're stupid, and tell > everyone who learnt from them as well. I'm in high school (gd. 11, junior) > and my physics teacher is always screaming at us for putting too many > decimal places or having them inconsistent. There are certain situations > where adding a ±1 is too cumbersome and / or clumsy, so you can specify the > accuracy using just decimal places. > This, again, is a presentation issue, and is irrelevant to the intricacies of fixed-point arithmetric. > For example, 5.00 would mean pretty much spot on 5 (anywhere from 4.995 to > 5.00499), wheras 5 could mean anywhere from 4.5 to 5.499. > > Please, let's quit this dumb argument. We all know that thermistors and > other types of cheap temperature gauges are very inaccurate, and I don't > think expensive thermocouples will make it into computer sensors very soon. > Plus, who the hell could care whether their chip is at 45.4 or 45.5 degrees? > Does it really matter? A difference of 0.1 will not decide whether your > chip will fry. Does it really matter NOW? No. However, 1 cK is a convenient unit and a good use of bits. Can we guarantee it won't matter in the future, especially not on a CPU which may very well require complex algorithms to eke out optimal performance in a thermally-challenged environment (more than just simple trip points.) Now it gets interesting! I have actually seen, in the lab, an algorithm which required complex guesswork, because it required information below the noise level of the sensor (and yes, it *is* possible to obtain that information.) -hpa -- at work, in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt