From owner-freebsd-questions@FreeBSD.ORG Fri May 11 01:51:32 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 666B216A405 for ; Fri, 11 May 2007 01:51:32 +0000 (UTC) (envelope-from youshi10@u.washington.edu) Received: from mxout3.cac.washington.edu (mxout3.cac.washington.edu [140.142.32.166]) by mx1.freebsd.org (Postfix) with ESMTP id 4461513C46C for ; Fri, 11 May 2007 01:51:32 +0000 (UTC) (envelope-from youshi10@u.washington.edu) Received: from hymn03.u.washington.edu (hymn03.u.washington.edu [140.142.12.169]) by mxout3.cac.washington.edu (8.13.7+UW06.06/8.13.7+UW07.03) with ESMTP id l4B1pVbw008931 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Thu, 10 May 2007 18:51:31 -0700 Received: from localhost (localhost [127.0.0.1]) by hymn03.u.washington.edu (8.13.7+UW06.06/8.13.7+UW07.03) with ESMTP id l4B1pV51029497 for ; Thu, 10 May 2007 18:51:31 -0700 X-Auth-Received: from [192.55.52.4] by hymn03.u.washington.edu via HTTP; Thu, 10 May 2007 18:51:31 PDT Date: Thu, 10 May 2007 18:51:31 -0700 (PDT) From: youshi10@u.washington.edu To: freebsd-questions@freebsd.org In-Reply-To: <1178814197.1231.48.camel@zoot.mintel.co.uk> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-PMX-Version: 5.3.1.294258, Antispam-Engine: 2.5.1.298604, Antispam-Data: 2007.5.10.182333 X-Uwash-Spam: Gauge=IIIIIII, Probability=7%, Report='NO_REAL_NAME 0, __CP_MEDIA_BODY 0, __CT 0, __CT_TEXT_PLAIN 0, __HAS_MSGID 0, __MIME_TEXT_ONLY 0, __MIME_VERSION 0, __SANE_MSGID 0, __STOCK_PHRASE_7 0, __STOCK_SUBJ_9 0' Subject: Re: WOW! {Or Holy whatever} X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 May 2007 01:51:32 -0000 On Thu, 10 May 2007, Tom Evans wrote: > On Thu, 2007-05-10 at 08:49 -0700, Garrett Cooper wrote: >> A good rule of thumb: Don't buy a video card with more RAM than 1/8 to >> 1/4 of the system RAM, because the RAM is shared with the system RAM, >> which means you have less overall system RAM to use for apps. >> >> -Garrett > > Er? Whilst I agree with the sentiment (low end graphics cards with 512MB > of RAM are solely there to rip off the unwary), that is complete tosh. > > Some cards dont have much/any onboard dedicated RAM; instead they use > system memory. Examples of these are nvidia cards labelled 'TC' (Turbo > Cache), most (all?) integrated intel video chipsets. > > The other issue is on i386. 32-bit systems have 4GB of address space to > use. Since you want to be able to address the graphics cards memory, > some of this address space is allocated so the OS can address the > memory. This means that if system RAM + video RAM > 4 GB, some of the > system RAM is unaddressable. That itself is a bit simplistic (its not 4 > GB, its ~3.5 GB, for various reasons.) > > The main point is that if you have a system with 1 GB of system RAM and > put in a graphics card with 640 MB of video RAM, you still have 1 GB of > system RAM to play with, even though you have gone over 1/4 of the > system RAM. > > Tom Assumption: ( System memory < 2 GB ) & ( Card is AGP ). I think Robert is correct because AGP needs DMA whereas (and I'm not 100% on this point) PCI-e doesn't. Most of the statement above was based on DMA and preallocated memory provided to the video card. -Garrett