From owner-freebsd-current@FreeBSD.ORG Fri Jul 2 15:57:11 2004 Return-Path: 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 1BAEF16A4CE; Fri, 2 Jul 2004 15:57:11 +0000 (GMT) Received: from mailhub.sweetdreamsracing.biz (mailhub.sweetdreamsracing.biz [66.92.171.106]) by mx1.FreeBSD.org (Postfix) with ESMTP id 929E343D54; Fri, 2 Jul 2004 15:57:08 +0000 (GMT) (envelope-from culverk@sweetdreamsracing.biz) Received: by mailhub.sweetdreamsracing.biz (Postfix, from userid 80) id 83B21175; Fri, 2 Jul 2004 11:44:17 -0400 (EDT) Received: from 141.156.69.109 ([141.156.69.109]) by www.sweetdreamsracing.biz (Horde) with HTTP for ; Fri, 2 Jul 2004 11:44:17 -0400 Message-ID: <20040702114417.yi3484ck0k0kcco8@www.sweetdreamsracing.biz> Date: Fri, 2 Jul 2004 11:44:17 -0400 From: Kenneth Culver To: questions@freebsd.org, current@freebsd.org References: <36u63c$231i65@mxip07a.cluster1.charter.net> <20040629103106.gpw4kwscsg88k0c8@www.sweetdreamsracing.biz> <20040629181248.S54069@carver.gumbysoft.com> <20040630011735.8mv40og88c4goko8@www.sweetdreamsracing.biz> <20040702152352.GB78489@dragon.nuxi.com> In-Reply-To: <20040702152352.GB78489@dragon.nuxi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Disposition: inline Content-Transfer-Encoding: 7bit User-Agent: Internet Messaging Program (IMP) 4.0-cvs Subject: Re: AMD64 vs i386 for FreeBSD X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 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: Fri, 02 Jul 2004 15:57:11 -0000 Quoting David O'Brien : > On Wed, Jun 30, 2004 at 01:17:35AM -0400, Kenneth Culver wrote: >> Quoting Doug White : >> >Me either. -current actually supports running i386 binaries in amd64 mode. >> >Thats one of the processor's features. :-) >> >> >You can't run amd64 binaries when booted into an i386 OS, of course. >> >> Yeah you can run x86 but you cant' go into regular 32 bit mode that's all. > > ENOPARSE, can you please restate this? I think what I meant is that once the kernel puts the CPU into "amd64" mode, it can't go back into regular x86 mode. It can run x86 binaries but it's not fully back in x86 mode, and I think some of the x86 instructions are gone in 64-bit mode, so it has to emulate them somehow. From what I understand 32-bit binaries run slightly slower when the cpu is in 64-bit mode because of this. From what I've read, you can't make a kernel go back into normal x86 mode until you reboot. You probably know about all this better than I do, it's been a long time since I read any tech specs for the cpu. Ken