Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757525AbXLJMKB (ORCPT ); Mon, 10 Dec 2007 07:10:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755473AbXLJMJw (ORCPT ); Mon, 10 Dec 2007 07:09:52 -0500 Received: from smtpq2.tilbu1.nb.home.nl ([213.51.146.201]:39778 "EHLO smtpq2.tilbu1.nb.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753763AbXLJMJw (ORCPT ); Mon, 10 Dec 2007 07:09:52 -0500 Message-ID: <475D2C37.6010809@keyaccess.nl> Date: Mon, 10 Dec 2007 13:08:23 +0100 From: Rene Herman User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Krzysztof Halasa CC: Pavel Machek , Andi Kleen , Alan Cox , "David P. Reed" , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops References: <475879CD.9080006@reed.com> <20071207160439.71b7f46a@the-village.bc.nu> <20071209125458.GB4381@ucw.cz> <20071209165908.GA15910@one.firstfloor.org> <20071209212513.GC24284@elf.ucw.cz> <475CBDD7.5050602@keyaccess.nl> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -1.0 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1318 Lines: 37 On 10-12-07 12:30, Krzysztof Halasa wrote: > Rene Herman writes: > >> Alan, did you double-check that 8 us? I tried to but I seem to not >> have trustworthy documentation. > > I remember 16-bit CPU-driven ISA was able to do 2-3 MB/s transfers, > that means at least 1 Maccesses/second = up to 1 microsecond/access. Yes, the thing is that I'm fairly convinced that an out to an unused port takes sort of exactly 1 us (8 cycles at 8 MHz). That's what I've always known it to be at least and have taken as the point. The same's also said here for example: http://tldp.org/HOWTO/IO-Port-Programming-4.html as well as in the bit of MINIX source in an earlier version of this thread: http://lkml.org/lkml/2002/3/14/194 Oh, in fact, a few older posts by Alan himself: http://lkml.org/lkml/2002/3/15/2 http://lkml.org/lkml/2003/9/22/263 I'm not a hardware person as the level of actual electrical signals but if an earlier instance of Alan is disagreeing with the current one as well, I guess it's halfway safe to join that one... Rene. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/