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question about crossfire and overclocking

Viper87227

Viper87227

Fully [H]
Joined
Jun 2, 2004
Messages
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Should be an easy one but Google was not helpful. If you have two cards do they have to be overclocked evenly? I have a 4890 that has aftermarket cooling and volt mods and overcloks very well and another non reference xfx card that does not overcloks well. If I put them together will the better card get held back?
 
It should be the same concept as adding ram of different speed, the cards' speed would be as fast as it's slowest card.
 
I found this to be true as well...

I have 2 Matrix 2GB 5870s- 1 OCs to 1009 with no overvolting, while the other only hits 940. So my default OC in Crossfire has to be 940 for both. Just nature of the beast, I guess... :cool:
 
Actually, you don't need evenly overclocked cards to Crossfire them. Although the software makes you overclock them together, you can flash whatever clocks you want them to run at in the cards' BIOSes and they'll still run in CF. However, they still have to work together, so that doesn't mean one card still won't hold back the other (though overhead or otherwise). I'm saying it's possible, but I have no idea about the performance impact. For comparison, tunning a 5870 and a 5850 in CF gives noticeable performance improvement, and your two cards would be much closer: http://www.techreaction.net/2010/06/30/blog-asus-5870-xfx-5850-crossfirex-mismatch/ (remember that Crossfire performance in general was borked in 10.6 with Bad Company 2, so I wouldn't consider that).
 
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