From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.201]) by ozlabs.org (Postfix) with ESMTP id 4D4682BEA0 for ; Sat, 18 Dec 2004 08:23:00 +1100 (EST) Received: by wproxy.gmail.com with SMTP id 67so183080wri for ; Fri, 17 Dec 2004 13:22:59 -0800 (PST) Message-ID: <69304d11041217131620036e56@mail.gmail.com> Date: Fri, 17 Dec 2004 22:16:19 +0100 From: Antonio Vargas To: Kendall Bennett In-Reply-To: <41B9A33A.26557.5DDD7EC8@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII References: <41B9A33A.26557.5DDD7EC8@localhost> Cc: linuxppc-dev@ozlabs.org Subject: Re: Write Combining for PowerPC? Reply-To: Antonio Vargas List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 10 Dec 2004 13:23:06 -0800, Kendall Bennett wrote: > Hi Guys, > > We are working on some PowerPC machines and noticed that the boxes don't > appear to support the equivalent of Write Combining that we get on x86 > boxes. Copies to Video Memory on our Motorola Sandpoint box run about > 10Mb/s, which is terribly, terribly slow! > > Does anyone know if it is possible to do something similar to Write > Combining for the PowerPC architecture, to speed up CPU access to the > linear framebuffer? Part of the problem is that for video overlay support hmmm... G4 processors will do write-combining when you write two cachelines just one after the other... there is a write-queue on the cpu and when there is 1 write on the queue and you add another one for the next cacheline, it will automatically merge the write. Also, if you manage to complete a sector, then he knows you don't need to read-then-write the memory and just issues a "kill-this-cacheline" on the bus instead of "please-i-need-exclusive-access-for-this-cacheline" > (not motion compensation) you have to dump the entire YUV frame into > video memory for the hardware overlay, and even on a 1GHz PPC box playing > an MPEG2 stream is not possible as X takes up over 80% of the CPU just to > copy the YUV data to video memory! > > Obviously bus mastering will help solve this problem, but it would be > better if there was a way to enabling faster CPU access to the > framebuffer as well. bus mastering is DMA-ing from system memory to gfxcard memory? > Regards, > > --- > Kendall Bennett > Chief Executive Officer > SciTech Software, Inc. > Phone: (530) 894 8400 > http://www.scitechsoft.com > > ~ SciTech SNAP - The future of device driver technology! ~ > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-dev > -- Greetz, Antonio Vargas aka winden of network http://wind.codepixel.com/ Las cosas no son lo que parecen, excepto cuando parecen lo que si son.