So did our little experiment work? You bet. Without any issues whatsoever. The Catalyst software suite picked up both cards (in this case an R9 280X and HD 7970 GHz Edition), detected a Crossfire compatible system and we were off to the races. The only small hiccup was a slight reduction in the GHz Edition’s core speed to compensate for the lower-clocked R9 280X. Overclocking would have solved this discrepancy in an instant.
Below, we’ve included some scaling percentage comparisons between the HD 7970 GHz Edition / R9 280X hybrid setup and a standard HD 7970 GHz Edition Crossfire setup. Remember, a standard HD 7970 3GB would work here as well.
Not only do these results point to excellent Crossfire scaling across a large number of games (minus Assassin’s Creed for which profiles still don’t exist) but they also represent hope for HD 7970 users who many not have the cash to buy another card right now. This isn’t an error on AMD’s part either that will be patched in the future; the multi-generational compatibility was fully intentional and will continue into the future. That’s great news for Radeon users.
We should also mention that “mixed” Crossfire compatibility between HD 7000-series parts and their updated R-series siblings spans AMD’s lineup. For example, the R9 270X can be paired up with an HD 7870 GHz and the R7 260X works happily alongside an HD 7790. Clock speeds will be tied at the hip in every instance with the slowest card dictating final frequencies but as we mentioned before, overclocking will mitigate any performance shortfall.
AMD could have easily locked out this compatibility in an effort to boost sales of their new cards. They didn't do that. Instead, they erred on the side of providing the best possible experience for their current and future customers. It also gives them a leg up on the NVIDIA competition since GeForce cards have never supported so-called “mixed” SLI even if two cards use the same core design. For example, a GTX 770 –which is essentially a rebranded and overclocked GTX 680- can’t be placed in SLI alongside its predecessor. In some ways at least, this makes Crossfire more versatile than SLI.
While inter-generational compatibility may not be utilized by the lion’s share of gamers, AMD should be applauded for allowing their current users to retain a clear upgrade path without discarding one of their most expensive components.
Full Article
http://www.hardwarecanucks.com/foru...crossfire-r9-280x-hd-7970-scaling-tested.html
Good results but they're a little bit cpu bottlenecked in a couple of these benchmarks at 1080P, otherwise scaling would be even better in a couple of these titles. Hitman Absolution stands out as one such title that requires a good overclock to achieve 90%+ scaling according to my own testing at 1080P.
