CrossFire Question

[Vhacia]

Hello, I have a question about CrossFire

I have a radeon 7850 OC at 1150/1300 and was just about to buy another one to CrossFire them both together. While I was browsing trying to find crossfire reviews I remembered that the 7850 and 7870 are both the same Pitcairn GPU.

I was wondering if I CrossFired a 7850 and 7870 would the 7870 lose its ability to use its extra cores and texture units or would only clock rates be affected (As my 7850 is currently faster than a stock 7870 so clock speeds are not a problem).

Any help would be appreciated

 

[plasmaj12345]

Although they can be crossfired, microstuttering is a huge issue here when crossfiring two different cards even though they are part of the same series. Just get another 7850. AMD's crossfiring in the same series technology isn't that great yet, but may be for future generations.

 

[Vhacia]

Thanks for the reply, I was going to go with a 7850 in the first place, just wanted to know about the 7850 and 7870 together.

 

[Spaniard United]

I would assume they even out. The 7870 is working in conjunction with the 7850 and therefore will only be able to do what the 7850 can do. Clock speeds certainly, but even down to architecture of the board, if they are crossfired, I wouldn't think the 7870 would be allowed to outpace the 7850, it would instead only use what the 7850 had available.

Just my thoughts though ... not sure.

 

[Vhacia]

Yea, I havent really found any reviews on crossfire with 2 different cards. Wondered what would happen

 

[Spaniard United]

Yeah the only information Ive seen on different GPUs usually references core clocks and memory clocks/size.

Given that the only true difference between a 7870 and a 7850 (since you can OC the former to match clocks with the latter) is the board and the features enabled therein. I would assume as this is also a deciding factor in the performance of each card, that it would therefore be limited to the lesser of the two cards as to how much of its board it can utilize.

Theoretically it makes sense, but reality is often a different case.

 

[Vhacia]

And considering that the Crossfire drivers struggle with two of the same GPU's I wonder how they cope with two different ones.

 

[quilciri]

Although they can be crossfired, microstuttering is a huge issue here when crossfiring two different cards even though they are part of the same series. Just get another 7850. AMD's crossfiring in the same series technology isn't that great yet, but may be for future generations.

Actually, microstutter with 2 cards setups is, for the most part, a thing of the past. Turning off v-sync (or adaptive v-sync for Nvidia) virtually eliminates all microstutter.

http://www.tomshardware.com/reviews/radeon-hd-7990-devil13-7970-x2,3329-11.html