From owner-freebsd-current@FreeBSD.ORG Mon Oct 31 02:52:10 2005 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 1281616A41F; Mon, 31 Oct 2005 02:52:10 +0000 (GMT) (envelope-from freebsd@deadcafe.de) Received: from deadcafe.de (deadcafe.de [81.169.162.144]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5FC4843D49; Mon, 31 Oct 2005 02:52:09 +0000 (GMT) (envelope-from freebsd@deadcafe.de) Received: from dialin.t-online.de (p54A5CAB2.dip.t-dialin.net [84.165.202.178]) by deadcafe.de (8.13.4+Sun/8.13.4/Rock) with ESMTP id j9V2paHY024613 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 31 Oct 2005 03:51:39 +0100 (CET) Received: from [172.23.7.254] (doom.rock.net [172.23.7.254]) by dialin.t-online.de (8.13.4+Sun/8.13.4/Rock) with ESMTP id j9V2pJSH042483; Mon, 31 Oct 2005 03:51:20 +0100 (CET) Message-ID: <436586A6.4090907@deadcafe.de> Date: Mon, 31 Oct 2005 03:51:18 +0100 From: Daniel Rock User-Agent: Mozilla Thunderbird 1.0.7 (Windows/20050923) X-Accept-Language: de-DE, de, en-us, en MIME-Version: 1.0 To: "M. Warner Losh" References: <20051030093718.GE39253@dragon.NUXI.org> <4364D90F.3090205@samsco.org> <20051030195936.GZ4115@funkthat.com> <20051030.161606.65680605.imp@bsdimp.com> In-Reply-To: <20051030.161606.65680605.imp@bsdimp.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=1.8 required=5.5 tests=FORGED_RCVD_HELO, RCVD_IN_NJABL_DUL,RCVD_IN_SORBS_DUL autolearn=disabled version=3.0.4 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on deadcafe.de X-Spam-Level: * X-Mailman-Approved-At: Mon, 31 Oct 2005 12:48:04 +0000 Cc: Alexander@Leidinger.net, gurney_j@resnet.uoregon.edu, freebsd-current@freebsd.org, davidxu@freebsd.org Subject: Re: TSC instead of ACPI: powerd doesn't work anymore (to be expected?) 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: Mon, 31 Oct 2005 02:52:10 -0000 M. Warner Losh schrieb: > Actually, ioport reads can be faster than the 1us that's widely > quoted. ioport reads can be as fast as ~125ns (2 cycles at 16MHz). > However, experience has shown that they are rarely this fast. I've > seen 8MB/s pio over the pci bus on some custom hardware we have, which > 2Mreads/sec which is about 500ns per read. I think that the pci > hardware that I was reading had a few extra wait states... According to "Software Optimization Guide for AMD64 Processors": http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/25112.PDF the "in" machine instructions have a latency of ~180 clock cycles. But this will be only the lower theoretical limit. Daniel