Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759572AbZAHPLS (ORCPT ); Thu, 8 Jan 2009 10:11:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752129AbZAHPLF (ORCPT ); Thu, 8 Jan 2009 10:11:05 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:43937 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750928AbZAHPLD (ORCPT ); Thu, 8 Jan 2009 10:11:03 -0500 Date: Thu, 8 Jan 2009 16:10:46 +0100 From: Ingo Molnar To: Alan Cox Cc: Peter Zijlstra , Jiri Kosina , Adam Osuchowski , linux-kernel@vger.kernel.org, Nick Piggin , Thomas Gleixner , "H. Peter Anvin" Subject: Re: Is 386 processor still supported? Message-ID: <20090108151046.GK18120@elte.hu> References: <20090108120338.6b8b4567@zonk.pl> <1231424025.11687.447.camel@twins> <1231424833.11687.452.camel@twins> <20090108150448.2393aeb0@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090108150448.2393aeb0@lxorguk.ukuu.org.uk> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1464 Lines: 36 * Alan Cox wrote: > > > Hmm. Where in Kconfig is SMP for M386 not allowed? > > > > Dunno, kconfig is too much of a jungle for a simple person like me ;-) > > > > But afaik i386 (and possibly i486) don't support nearly enough for a > > modern SMP system. > > > > Alan used to have i486-smp I think, one of the very few ever made. > > The first systems that supported the Intel MP standard are 486 based > with external APIC. The prior systems used various proprietary MP > interfaces from the simple stuff in the Compaq (which Linux doesn't > support as Compaq refused to allow Thomas Radke to contribute it) to the > fairly extreme end of things with the Sequent boxes. > > In addition our FPU emulation and some of our handling for x86 > processors where we have to do the WP bit in software is also not SMP > safe. > > So our minimal spec for SMP is probably 486DX + external Intel APIC. > > In practice I doubt there is a single Intel APIC type 486 SMP box on the > planet running Linux (or quite possibly running at all) yeah, that's very likely true. I think we could eliminate some of the SMP complications by requiring cmpxchg presence for CONFIG_SMP, agreed? Ingo -- 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/