From owner-freebsd-current Wed May 19 12:31: 7 1999 Delivered-To: freebsd-current@freebsd.org Received: from dingo.cdrom.com (dingo.cdrom.com [204.216.28.145]) by hub.freebsd.org (Postfix) with ESMTP id 7B4C714BDE for ; Wed, 19 May 1999 12:31:03 -0700 (PDT) (envelope-from mike@dingo.cdrom.com) Received: from dingo.cdrom.com (localhost.cdrom.com [127.0.0.1]) by dingo.cdrom.com (8.9.3/8.8.8) with ESMTP id MAA00410; Wed, 19 May 1999 12:27:31 -0700 (PDT) (envelope-from mike@dingo.cdrom.com) Message-Id: <199905191927.MAA00410@dingo.cdrom.com> X-Mailer: exmh version 2.0.2 2/24/98 To: Luoqi Chen Cc: mike@smith.net.au, ctapang@easystreet.com, current@FreeBSD.ORG, jerry.alexandratos@perspectives.net, jlemon@americantv.com Subject: Re: FBSDBOOT.EXE In-reply-to: Your message of "Wed, 19 May 1999 13:29:56 EDT." <199905191729.NAA14869@lor.watermarkgroup.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 19 May 1999 12:27:31 -0700 From: Mike Smith Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > Not at all. If there's 640k chopped off the end of eg. 128M of > > physical memory, you'd have to use a 64M segment, a 32M segment, a 16M > > segment, an 8M segment, a 4M segment, a 2M segment, a 1M segment, a > > 256k segment and a 128k segment to map it accurately. That's 9 > > variable MTRRs, and the P6 only has 8. > > > No you don't need that many, fixed MTRRs take precedence over variable MTRRs, > so you can just use one variable segment covering 0-128M and override with > fixed MTRRs in the low memory area. I specifically said "640k chopped off the end", referring to the possibly non-aligned _end_ of physical memory. The issue here is that the BIOS will tell us how much memory we are _allowed_to_use_, which is not always the same as the amount of physical memory present in the system. Some memory may be (is sometimes) reserved for use by eg. APM/ACPI. We fare badly at the moment on these systems because we ignore this and use all the memory we can find. -- \\ The mind's the standard \\ Mike Smith \\ of the man. \\ msmith@freebsd.org \\ -- Joseph Merrick \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message