Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756130AbXLJLbG (ORCPT ); Mon, 10 Dec 2007 06:31:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753338AbXLJLa5 (ORCPT ); Mon, 10 Dec 2007 06:30:57 -0500 Received: from khc.piap.pl ([195.187.100.11]:60858 "EHLO khc.piap.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753299AbXLJLa4 (ORCPT ); Mon, 10 Dec 2007 06:30:56 -0500 To: Rene Herman 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> From: Krzysztof Halasa Date: Mon, 10 Dec 2007 12:30:53 +0100 In-Reply-To: <475CBDD7.5050602@keyaccess.nl> (Rene Herman's message of "Mon, 10 Dec 2007 05:17:27 +0100") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1210 Lines: 29 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. Perhaps IO ports accesses were slower than memory? But 8-12 times? Perhaps port 0x80 was using (slower) 8-bit timings? Bus-mastering ISA cards were able to do ca. 5 MB/s with 8 MHz (10 MHz?) clocking, some old machines didn't like it. Googling suggests that a slave access on 8-bit ISA bus was taking 6 cycles by default (including 4 wait states), 16-bit - 3 cycles (with 1 WS). Respectively 0.75 us and 0.375 us, and 0.25 us for 16-bit 0WS memory access (with standard 8 MHz clock). These values could be changed with BIOS setup, and devices could use 0WS or I/O CHRDY signals if they didn't like the defaults (dir 0WS mean 1 WS for 8-bit devices?). -- Krzysztof Halasa -- 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/