From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Smirl Subject: Re: [Linux-fbdev-devel] Re: radeon, apertures & memory mapping Date: Sun, 13 Mar 2005 12:56:26 -0500 Message-ID: <9e4733910503130956401e1107@mail.gmail.com> References: <1110677744.19810.80.camel@gaston> <20050313082216.GA7362@sci.fi> <1110705646.14684.126.camel@gaston> <20050313103936.GA11002@sci.fi> <1110715499.14684.132.camel@gaston> <9e473391050313081937cde207@mail.gmail.com> <20050313174714.GA15871@sci.fi> Reply-To: Jon Smirl Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable In-Reply-To: <20050313174714.GA15871@sci.fi> Sender: dri-devel-admin@lists.sourceforge.net Errors-To: dri-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="iso-8859-1" To: linux-fbdev-devel@lists.sourceforge.net, Benjamin Herrenschmidt , Jon Smirl , dri-devel@lists.sourceforge.net, xorg@lists.freedesktop.org On Sun, 13 Mar 2005 19:47:14 +0200, Ville Syrj=E4l=E4 wrot= e: > I don't understand why we have "GART memory" anyway. It's just main memor= y > and I don't see any point going through the GART to access it with the > CPU. Only the graphics card needs to use the GART. I see no need to for the CPU to go through the GART either. The main CPU page tables can provide the same rearranging that the GART does. We do need specially marked GART memory because of caching issues. If the CPU writes to GART RAM the write may still be on the CPU chip in a cache. We have to make sure it gets pushed into physical memory so that the GPU can see it. The best model would be to chuck the AGP/PCI Express interface on the board and have a hyperchannel instead. Hyperchannel provides full cache consistency without all of these flushing problems. The GPU really is another specialized CPU, give it a CPU class memory interface. --=20 Jon Smirl jonsmirl@gmail.com ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click --