Date: Wed, 19 May 1999 12:27:31 -0700 From: Mike Smith <mike@smith.net.au> To: Luoqi Chen <luoqi@watermarkgroup.com> Cc: mike@smith.net.au, ctapang@easystreet.com, current@FreeBSD.ORG, jerry.alexandratos@perspectives.net, jlemon@americantv.com Subject: Re: FBSDBOOT.EXE Message-ID: <199905191927.MAA00410@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 19 May 1999 13:29:56 EDT." <199905191729.NAA14869@lor.watermarkgroup.com>
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> > 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 messagehome | help
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