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HD 4850 1gb & 512mb crossfire

Last response: in Graphics & Displays
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May 26, 2011 3:13:53 AM

ok i have a FEW problems and questions pertaining to the cross-firing of two cards


an xfx 1gb hd 4850

and a gigabyte 512mb hd 4850, both have after market coolers

now for the questions:

does it matter which one i put where? i put the xfx 1gb as primary because it runs hotter, i figure putting it under the cooler card would be dumb

will i have issues with crossfiring these two? i recall reading the xfx card i have is designed around a mobile chip, dont know if that will mess with my configuration

how many bridges do i need to fully optimize cross firing? currently i have only one on it, i have an x38 mobo with pcie 2.0 x16 on both lanes, a hx750 corsair psu

how would i overclock each card individually? should i have crossfire enabled or disabled when i do this?

also im having a few problems... i get jittery in a few games [i have the latest drivers], and when it is enabled, FEAR blacks out... when it ISNT though, fear works perfectly and i also see a performance boost! WTH?also, i see NO performance boost on bfbc2 for steam... =[

i havent done crossfire in a very long time, and although i feel like i can answer these questions, i figure i maybe wrong since im having so many problems... i ran the newer card by itself, and it worked great, and the older gigabyte one ive been using for a few years, never caused me a problem... someone?? anyoneee?? tyyy : :ange: 

lemme just put my rig info here to prevent further questioning about my rig

e8400 @ 3.6
hd 4850 1gb and 512mb
4gb ddr2 800
maximus formula se x38 motherboard
hx750 watt corsair PSU
150gb raptor hdd

its old, but its chuggin along still quite well! :na: 
May 26, 2011 6:47:27 AM

1) Doesn't matter
2)No,brands don't matter so there shouldn't be any problem;however, overall you'll have 512MB memory
3)One should suffice
4)Enabled, and you can do it with MSI afterburner
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May 26, 2011 5:26:13 PM

wow thanks!!!! anyone have solutions for my other problems? perhaps there's an older more stable driver some one can recommend...
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May 26, 2011 6:18:02 PM

ATI unlike Nvidia does not allow differential clocks and overclocking in crossfire. In sli this is very different. You can overclock but it will affect the other card so clocks are matched. As for drivers you got plenty of choices and the drivers for these cards are lot better than more current Radeon 5k and 6k series. Current drivers seam to be ok for Radeon 3k and knowing how the 4k series are you should have few problems if any at all except for ccc.
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Best solution

May 26, 2011 6:55:16 PM

I'm not sure how well this will work.

On one hand, you'll get better framerates, on the other hand you can only get up to 512MB of Video Memory because Crossfire defaults to the lowest common denominator. Video Memory is not "added" together in Crossfire, and it's too complicated to discuss the details here. The last 512MB of the 1GB of VRAM on the first card can not be used.

I don't have Crossfire, but I think you can switch between single-card and Crossfire mode in software. I recommend having the 1GB card hooked up to your monitor and be on top of the other card.

I recommend comparing framerates (FRAPS) and quality settings in a few high-end games with just the 1GB card active (non-Crossfire) and both in Crossfire.

I'm not sure if you would find a game that would run better with the single 1GB card due to it's extra memory rather than being in Crossfire. It's possible a game might have sufficient GPU processing power with a single card but desire more than 512MB of VRAM.
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June 5, 2011 2:22:38 PM

Best answer selected by eklipz330.
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