Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755362AbXI1T3V (ORCPT ); Fri, 28 Sep 2007 15:29:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751613AbXI1T3O (ORCPT ); Fri, 28 Sep 2007 15:29:14 -0400 Received: from mail.tmr.com ([64.65.253.246]:33565 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751547AbXI1T3N (ORCPT ); Fri, 28 Sep 2007 15:29:13 -0400 Message-ID: <46FD5707.9040807@tmr.com> Date: Fri, 28 Sep 2007 15:33:27 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: Andi Kleen CC: "Maciej W. Rozycki" , Peter Fordham , linux-kernel@vger.kernel.org Subject: Re: fpu IO port reservation (arch/i386) References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1546 Lines: 37 Andi Kleen wrote: > "Maciej W. Rozycki" writes: > >> Hi Peter, >> >>> Does anybody know why we reserve this range of IO ports for 'fpu'? >>> AFAIK from all the IO maps I can find on the internet for various x86 >>> chipsets only 0x00f0 is actaully ever used. >> There are two ports used: 0xf0 is the busy latch reset and 0xf1 is the >> coprocessor reset. They are legacy ports resulting from the interesting >> way the FPU has been wired by IBM in their PC design. > > Was it really needed on 386s? I didn't think there was a IBM 386 PC. There were 386 PC clones for sure, and they almost certainly needed it and still do. IBM was doing the MCA thing at that time and it was a wonderful time for the clone makers. > >> None of them is >> used by Linux for i486 and newer systems, which can support the FPU in its >> native configuration. > > I can remove it from x86-64 at least. > AFAIK you are just right, I'm pretty sure there will be systems needing it for 386 and 486, and maybe the old Pentium systems as well. A lot of system vendors wanted it so software for the old systems would still work. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot - 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/