StuG wrote:How did you come up with 1.5 generations? The 4870 has barely changed at all, and the 4890 is not a different generation.
Hence the .5. The 4890 was a tweak to the silicon of the RV770, moving transistors around and adding a grounding ring around the core. You can either view it as a separate product or an evolution of an existing product - it's a glass half/empty half full thing. The fact that they coexisted in the marketplace doesn't invalidate either view (the 9600 and 9700 Pro coexisted for a long time as well).
Also the 5770 I feel is a great value, considering the power envelope, size, and performance. Also, your comparing a card with fully matured drivers (4870) vs very new drivers (5770).The 4670 was crap when it came out, and now its much better. I expect much the same with the 5770, so to call it not a good value I feel is a mistake.
It's also preemptive to assume that there are going to be 'free' performance gains from driver optimizations. The 5770 has a very similar architecture (aside from a larger feature set) to the 4870, the same number of execution units, and a faster clockspeed, yet performs measurably (and noticeably) worse than the cheaper (but older) card. Because of that, I am hesitant to recommend it in its current state. Despite AMD's claims to the contrary, I can't help but think that cutting the memory bus in half has something to do with that*. A similar thing happened with the Radeon 9500 and 9600 (although they didn't have equal execution units in that case). The sad fact is that the 5770 is just barely fast enough to run modern games at 1920x1080 w 4xAA, so having DX11 is more of a checklist feature than real 'future-proofing'. Which is better - a full featured card that you (might) have to dial back effects to get a smooth experience (5770) or a cheaper, faster card that uses an older feature set (4870)? To be honest, that was too close to call for me - that's why I recommended the 5850 to the OP instead, but a $100 jump to move up from the 5770 is no light matter either.
That's not to say the 5770 (and 5850) don't have the advantage of lower power draw, quieter fans etc etc, but the OP specifically mentioned gaming as a priority. If he were discussing a HTPC build, then the 5750 would probably have been ideal.
* xbitlabs' overclocking figures with the 5850 - where
the 5850 reached wthin 2% the performance of the 5870 at the same clockspeed despite having a 10% shader unit penalty - also suggest to me that there is some bottleneck in the 5xxx cards that is keeping their shader units from hitting their full potential. Whether this is memory bandwidth or just immature drivers, it's too early to tell right now.
Wind, Sand and Stars.