From owner-freebsd-arch Sun Oct 13 11:56:44 2002 Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7064D37B401 for ; Sun, 13 Oct 2002 11:56:43 -0700 (PDT) Received: from conure.mail.pas.earthlink.net (conure.mail.pas.earthlink.net [207.217.120.54]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0C8A843E7B for ; Sun, 13 Oct 2002 11:56:43 -0700 (PDT) (envelope-from tlambert2@mindspring.com) Received: from pool0507.cvx40-bradley.dialup.earthlink.net ([216.244.43.252] helo=mindspring.com) by conure.mail.pas.earthlink.net with esmtp (Exim 3.33 #1) id 180nuR-0005qp-00; Sun, 13 Oct 2002 11:56:16 -0700 Message-ID: <3DA9C181.D36065CA@mindspring.com> Date: Sun, 13 Oct 2002 11:54:57 -0700 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: "M. Warner Losh" Cc: ticso@cicely.de, hch@infradead.org, wes@softweyr.com, dillon@apollo.backplane.com, vova@sw.ru, nate@root.org, arch@FreeBSD.org Subject: Re: Database indexes and ram References: <3DA954CF.98B0891A@mindspring.com> <20021013.060851.113437955.imp@bsdimp.com> <3DA9B4A8.194A02FC@mindspring.com> <20021013.120847.31902907.imp@bsdimp.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG "M. Warner Losh" wrote: > I think that's all irrelevant. Cards with 32bits can't go about 4GB. > It is a far more fundamental problem. Even 32bit cards in 64bit slots > can't do this. 64bit cards could DMA into anywhere in the first > 64bits of RAM, of course. I think we are in violent agreement. 8-). > I was confusing what you said with "The DMA is based on a virtual > address" which is not quite the same thing. Sorry if this was confusing; it was meant to reference the mappability of the physical memory, not that the DMA targetted anything but physical memory. You *could* "check DMAability" by having a target area at some address Q above 32 bits, and then checking to see if the data went there, or to the address Q & 0x00000000ffffffff instead. This would require you to pick your areas carefully. Ugly, ugly. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message