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how does ram work for games???

Last response: in Graphics & Displays
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December 8, 2008 2:13:42 AM

i have 2 pc's with 4GB ram but one shows 2.5GB in 3dmark06 and the second shows 2.8GB in 3dmark06. ok i was told that is because the gpu's take up some space, the first pc has SLI GTX 260-216 (3damark shows 2.5GB) and the second pc has 9800GX2 (3dmark shows 2.8GB). ok with the SLI GTX 260-216 the total ram of those 2 cards is 1.8GB (896 each, i rounded up), so my question is when i play a game i.e. crysis, it requires 2GB ram. so does crysis use the 1.8GB ram of the cards and then take the rest (200 or so MB) from the 2.5GB of windows? meaning is the 2.5GB like a backup to fill in the space thats left by the gpu's? and if i play a game that requires 1GB ram, the game doesnt need any of the 2.5GB because the gpu's have a total of 1.8GB? if someone could clear this up and help me understand that would be great and thanks alot because im really not getting this.

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a b U Graphics card
December 8, 2008 2:18:07 AM

Quick question: what is your OS? 32-Bit OSes have a limit on ram.
December 8, 2008 2:32:55 AM

yes its 32-bit and i know theres a limit which is why 3dmark shows 2.5GB, but windows does see all 4GB but thats not the question (right click on computer and it shows 4GB ram and E8400 @ 3.0GHz 3.6GHz), i want to know if the 2.5GB is like a reserve if the gpu's dont have enough ram. like crysis needs 2GB but SLI GTX 260-216 only have 1.8GB so it borrows some of the 2.5GB, thats what i would like to know.
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a b U Graphics card
December 8, 2008 2:33:20 AM

Games run like any other program. System memory is used for the program (the code) plus all the data used by the program. The GPU memory is used when it is needed for rendering. The program will use DirectX or OpenGL to manage the data, which is all kept in system memory and will be copied to the GPU memory when it is to be used for rendering a scene.

More GPU memory means that more data (like textures) can be kept on the card. So as DirectX is used to render difference scenes and objects, it will only copy the data to the GPU memory if it is not already there.

December 8, 2008 2:43:50 AM

If a game requires 2GB of RAM it is talking about motherboard RAM, not video RAM. Video RAM is the stuff in your video cards taking away allocated space from your system (motherboard) RAM. Windows 32 bit can normally only address 4GB of total RAM. It pickes the fastest 4GB. First off are your L1 and L2 caches on your CPU, then your video RAM, then your RAM on the motherboard.

Crysis requires 2GB of (motherboard)RAM but does not necessarily take up 2GB of (motherboard)RAM on your machine. IE windows takes a gig and Crysis takes another gig. The makers of Crysis and other video games know that windows will take up some RAM, your AV will take up some RAM etc. So they compensate for that in their requirement. The RAM on your video card is also used by Crysis and other video games and the amount needed may be listed under video card requirements, but not so much on the newer games as video card makers went crazy and have put ridiculous amounts of RAM on terrible video cards, thereby negating the method of determining a video cards abilities by the amount of vRAM it possessed.

Edit: I guess I missed the last two posts while typing this.
December 8, 2008 3:16:46 AM

as a quick intro i always find explaining things hard so when i find a good analogy i hang on to it... this one actually came from my history teacher...

memory is like a library when you go (turn on the computer) you have to find the books(data) you want from the shelves(hard drive) when you find them you take them to a table(motherboard RAM) and from their your mind can start to process the info....

with a GPU and a game it would be a little like this....

you now have 2 tables. 1 table has the encyclopedias related to the the game code(motherboard RAM). the other table has more picture books for the textures in a game.(GPU RAM)

i know this isn't perfect but it is pretty good

basicly their 2 gb recommendation is for motherboard memory. normally under the GPU they will say so much video memory and that is how much you want your graphics card(s) to have.

i hope this helps

if anyone can improve this analogy post it and i will check back in a day or 2
December 8, 2008 3:17:42 AM

ok thanks alot guys
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