From owner-freebsd-hackers Fri Aug 3 1:11:12 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from mass.dis.org (mass.dis.org [216.240.45.41]) by hub.freebsd.org (Postfix) with ESMTP id 177FB37B406; Fri, 3 Aug 2001 01:11:08 -0700 (PDT) (envelope-from msmith@mass.dis.org) Received: from mass.dis.org (localhost [127.0.0.1]) by mass.dis.org (8.11.4/8.11.3) with ESMTP id f733q9C01482; Thu, 2 Aug 2001 20:52:10 -0700 (PDT) (envelope-from msmith@mass.dis.org) Message-Id: <200108030352.f733q9C01482@mass.dis.org> X-Mailer: exmh version 2.1.1 10/15/1999 To: Kenneth Wayne Culver Cc: Julian Elischer , John Baldwin , freebsd-hackers@FreeBSD.ORG, craig , Terry Lambert , Rik van Riel Subject: Re: How to visit physical memory above 4G? In-reply-to: Your message of "Thu, 02 Aug 2001 14:55:28 EDT." Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Thu, 02 Aug 2001 20:52:09 -0700 From: Mike Smith Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > > No > > The space is linear in physical space and if you have PCI/64 > > capable devices they can access it all too. > > > > (In fact 64 bit addresses have been supported even in 32 bit wide PCI > > since day 1). > > OK, then what was that whole paging thing everyone was talking about, I > thought that was partially done in hardware on the chipset of the > motherboard... or was that completely in the operating system? Julian is on crack. DAC (Double Address Cycle) is a relatively recent addition to PCI that allows 32-bit cards with 64-bit savvy logic to talk to host memory using 64-bit target addresses. Older systems used a scatter-gather mechanism to present a virtualised view of the system's physical address space to the PCI bus (typically you'll see this in Alpha systems). -- ... every activity meets with opposition, everyone who acts has his rivals and unfortunately opponents also. But not because people want to be opponents, rather because the tasks and relationships force people to take different points of view. [Dr. Fritz Todt] V I C T O R Y N O T V E N G E A N C E To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message