I'm doing a new build for a PC. Just got a SLI mo-bo, and I noticed that my 9800 is no longer being sold anywhere. http://www.newegg.com/Product/Product.aspx?Item=N82E16814150323 - If you must know. There's only two more XFX cards like that, but they're on E-Bay or Tiger Direct. I don't trust E-Bay and I've heard bad things about Tiger Direct. Can I just get another 9800, say from EVGA, and run them like that? Or do they have to be twins?
Answer by MikeInVa · May 31, 2010 at 07:53 PM
Generally, and for the best possible outcome, both cards should be the same. There are a few exceptions, but they are rare and you would really want to do your homework before trying it yourself. Basically they need to have the same RAM and clocks. For example, a 7800 and 9800 can't be paired because they have different clocks. However you could pair two 7800GTX512 cards from different vendors since the memory and clocks are the same. In your case, the XFX could possibly be paired with one from eVGA or BFG, or even Galaxy if you can find one. Again, however, do your homework first to make sure or you'll end up wasting money.
Answer by Justin Green · May 31, 2010 at 09:11 PM
First of all only the actual GPU absolutely needs to match on both cards.
Prime example would be mixing a 9800GTX+ with a GTS 250 1024MB, by modifying the coolbits registry key you can force SLI between the two cards but the better card will automatically downclock or reduce the addressable VRAM to accommodate the other card.
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