At the online vault of leaked slideware known as ChipHell, one can find the confidential documents on the upcoming HD 6770 and HD 6750 graphics cards based on the Barts XT and Barts Pro chippery.
According to the slides (which have been heavily edited, possibly to remove the name of the OEM), the HD 6770 and 6750 look like they have the necessary silicon to stop the GTX 460 in its tracks...
The lower-end HD 6750 part, Barts Pro, although still in the mainstream/performance category, will feature 10 SIMD units running at a core clock speed of 700MHz through 725MHz with 1GB of GDDR5 1GB running on a 256-bit bus at 1GHz (4GHz effective). The power envelope will be sub-150W, according to the leaked slides. The HD 6750 should also offer a performance advantage over the HD 5770 Juniper card from last season.
The HD 6770, the higher-end Barts XT, clocks in at 850MHz, has the same memory specs, yet has 48 texture units and 960 shader cores, which will give it a slightly greater computing power and an overall performance edge of some 15% over its younger brother. In this case, the higher clock speed demands a bit more power, so the card is rated >150W.
The slides reveal nothing regarding the video output, which might be left up to the partners.
AMD is pushing the idea that both cards will outgun the GTX460 in both 768MB and 1GB incarnations (the prior having a 192-bit memory bus and the latter a 256-bit bus). You can also expect the pricing to at least match, if not undercut, Nvidia's prices
If all this pans out, we are looking at a relatively marginal performance gain (as expected) over the Juniper cards present in the previous generation. However, it remains to be checked whether highly edited slides such as these pan out. We've asked AMD about this, but we're expecting a "we can't comment" sort of reply in due course.
If you have a ChipHell account, you can give it a look.