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Is this true...


manOwar

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I was told by a friend that the computer can only use the graphic card memory from one card in SLI. :) Is this true? for example in my case, i have Dual GeForce Go 7900 GS 512mb in SLI. If what he says is correct i am only using 512mb instead of 1024mb! :P Is this really a fact & if so how can this be? :P

If anyone has heard of this before, i would really like to know if this fact or fiction.

Thank you in advance. :)

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I don't know why but yes, it will only use one of the cards video memory, but you have 512MB which is more than enough even for most modern games.

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actually is very true.

the second card in a SLI setup is only used to calcuate (NOT render) the scene, it does not need to load textures hence its memory isnt requird.

the textures are loaded into the parent card, there is no need to load the same data twice as this would be an absolute waste.

Parent: I've got the textures here, I'll draw every even numbered frame, you daughter shall draw every odd numbered frame, pass the data back to me and i'll add the texture data and send the finished result to the monitor.

SLI in split frame rendering works the same way. Because textures can cover the entire image, and because the workload is split evenly between the cards (NOT the actual image) then the cards would be rendering the same texture twice which is a waste of processing power and memory bandwidth.

One card handles the textures becasue its the most eficient way of handling such a huge amount of data.

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Hi, thanks for the info.

I was wondering though, which is better for games, SFR (Split-frame rendering) or AFR (Alternate-frame rendering). Also, should i force V-Sync On/Off or Application controlled?

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vsync off is always better as it produces a faster overall framerate (some games dont like vsync off and produce horrendous tearing, so leave it set to on for them)

as for SLI modes, your dont actually have a choice, each SLI profile hard sets the SLI type for each game. If you open the nvapps.xml file in your C:\Windows\System32 folder you'll see every game is pretty much set to AFR (alternate frame rendering)

you can use an app like nHancer to manually change a game profile, but SFR just doesnt appear to scale as well as AFR on most game engines which is a shame because SFR produces the least amount of input lag.

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Hmm, ok so i put v-sync on 'let application decide' but how do i change it for each app?

As for SFR/AFR, so if i force it on in the control panel it still wont put it on for games? And at the moment AFR is better for some reason? strange, because it sounds like SFR would produce better results. Is AFR still better when doing general things apart from gaming?

I attached a pic with my control panel settings could you tell me if i should change anything for the better... all those big words confuse me :)

settings.bmp

settings2.bmp

Edited by manOwar
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set vsync in control panel to OFF or FORCE OFF

setting the SLI setting in control panel only works for applications/games that dont have a profile in nvapps.xml

if a game has a profile in the nvapps.xml file then what ever you set in control panel is ignored and over-ridden by the profile.

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Hmm... ok thanks. For those that dont have a profile, what do you recommend A/SFR?

Also if you dont mind, whats the best way to install new drivers? Like uninstall the old one first then put the new one in? I just clicked the setup file without uninstalling anything :) I heard bits and pieces around the place, like cleaning the registry, doing something in safe or what not. Is there somewhere i can find a complete description of how to do it properly?

Thanks :)

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if you've nver had any problems simply clicking on the .exe file and install new drivers over old ones then i wouldnt concern yourself. some people are major paranoid about registry entires/old files etc. Ohers have genuine problems if they dont remove the old drivers completely. if your not having problems then dont worry.

normally, you can just remove the old drivers from Add/Remove Programs, reboot, install new drivers.

as for which SLI mode is best for games/apps with no profile, thats just a case of trial and error, set a SLI mode, run the game, check the fps your getting, change SLI mode and retest.

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most games have an inbuilt fps counter via a command line variable

eg.

UT engine games = stat fps

failing that download Fraps, that will give you an fps counter overlay for any game.

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Is there a way too find out all the commands in for a game? Im wanna check in crysis and in the witcher, any idea what the command is?

Thanks for all you help. :)

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