better than perfect scaling in cod4?

[natty1]

Just wondering why Anandtech thought it would be a good idea to test single cards in a different platform than Crossfire. I'm refering to the 4870 crossfire test where two cards score over twice as much as the single card. Obviously, it produced a result that looks artificially inflated.

 

[chewietobbacca]

I'll refer you to this post at beyond3d by Eric Demers who was a HW engineer for the R600 architecture

http://forum.beyond3d.com/show...p=1181705&postcount=62

As for super-linear performance, it's possible -- The actual amount of cache is increased as well as the number of functional units. That means that it's very possible for data to stay in cache longer in xfire, than in regular rendering on a single card. That will lead to performance higher than 2x.

On average, we are seeing scaling in the 1.75 ~ 1.85 range for xfire. Of course, this is at higher resolutions and/or higher settings.

So scaling > 2x is actually possible, but most games when optimized for CF will see 1.75-1.85x scaling due to the increased cache