From owner-freebsd-current Mon Jul 19 10:28:23 1999 Delivered-To: freebsd-current@freebsd.org Received: from hal-pc.org (hal-pc.org [204.52.135.1]) by hub.freebsd.org (Postfix) with ESMTP id 8BF8315149 for ; Mon, 19 Jul 1999 10:28:20 -0700 (PDT) (envelope-from jes@hal-pc.org) Received: from jason (206.180.128.29.dial-ip.hal-pc.org [206.180.128.29]) by hal-pc.org (8.9.1/8.9.0) with SMTP id MAA01752 for ; Mon, 19 Jul 1999 12:27:14 -0459 (CDT) Message-ID: <002b01bed20b$5547e1c0$0500a8c0@local.nullifier.dyn.ml.org> From: "Jason" To: References: <199907190516.HAA21639@dorifer.heim3.tu-clausthal.de> Subject: Re: Question about MTRR boot message Date: Mon, 19 Jul 1999 12:22:51 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2014.211 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2014.211 Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > BTW, is there a way to disable that MTRR stuff? Just to be > sure... And I really don't need it. > > Regards > Oliver Before you go any further worrying about this "just in case", there is nothing for you to worry about. Part of what the MTRR "stuff" does is it stops the L2 cache from cacheing that range of memory. This is typicaly used for video cards, as you have been told, because well, you really never read back from the video card's memory frame buffer, and if you did, for some strange reason, it would only result in a cache miss and would then have to be fetched from main memory. Since your L2 cache isn't wasting space on this area of memory, it can cache something more usefull, and thus give you a speed *increase*. Another part of what MTRR does is allow multiple overlapping writes to the same uncacheable memory range to be combined into a single write, with a good likely hood of a speed increase. Thus, MTRR is GOOD. - Jason To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message