Perhaps we were expecting too much, but the Radeon HD 5770 was a little underwhelming in our books. Where performance is concerned, we expected it to be positioned in between the Radeon HD 4890 and HD 4870, but our tests have shown that it was mostly
a smidge lower than the HD 4870 1GB editions; which puts it closer to the 512MB edition of the Radeon HD 4870. The Radeon HD 5770 was also no match for NVIDIA's GeForce GTX 275 and GTX 260+.
The results seem to indicate the shortcoming of the 128-bit memory bus that the 'mainstream' Radeon HD 5770 possesses. In fact, we were perplexed as to why the Radeon HD 5770 didn't receive a 256-bit wide memory bus like the Radeon HD 4870 did. Perhaps that's still the same silver lining that divides the mainstream from high-end graphics cards as has been the case for several years now. All things equal, we think that a memory bus upgrade would allow the Radeon HD 5770 to convincingly outperform the Radeon HD 4870.
However, while the Radeon HD 5770 might lack the firepower to take on the big boys, it does have a couple of other things going for it.
For one, it runs relatively cool even on a stock cooler and it has by far the best power consumption figures, which makes it energy efficient - something which the environmentally conscious should take note of.
So think of the new Radeon HD 5770 somewhat as a revised HD 4870 card that is much more environmentally friendly. Not to forget that it fully supports DirectX 11, which should come in handy as more DirectX 11 games slowly creep in to the market next year. Furthermore, it also boasts ATI's EyeFinity technology, which makes a triple monitor setup a possibility.
http://www.hardwarezone.com/articles/view.php?id=3036&cid=3&pg=1