In order to fully grasp the goals of the RV770, we'll take a snippet from Rick Bergman's, Senior Vice President and General Manager,  presentation about ATi's new strategy:

A Turning Point

Traditional GPU Strategy

A New Strategy

Scalable Design

It's obvious that the RV770 marks a turning point for ATi, the final departure from the "one monolithic GPU to rule them all" mentality. This very approach was probably the R600s undoing: things kept piling on during the design process, the chip kept getting larger, TDP was rising ... you can see where this is going. One could argue that the RV670 marked the beginning for this new strategy Mr. Bergman talks about, but we beg to differ: the two projects ran in parallel, with the RV670 being a refinement that allowed an early peek at how things would be tackled in the future, and the RV770 being built from the ground up to fit the new vision.

Looking at the last slide, one begins to realize that the goals for the RV770 generation were quite lofty: solid performance, accessible pricing, thermals that allow scaling the architecture upwards (the Ultra Enthusiast segment is important, in spite of its relatively low absolute volume - it's no good dominating the mainstream and eventually performance segments with a chip that's already too hot and too large for its own good, thus making it unfeasible for multi-GPU approaches meant to cater to that very Ultra Enthusiast mentality). Did it all materialize? Time to find out - here's the opening slide from Scott Hartog's presentation:

Now we have an idea of what to expect: a chip aimed at more than doubling the processing power of ATi's previous generation; one that addresses one of the biggest weak points of the whole R600 generation, namely AA performance, whilst being better suited for GPGPU tasks and maintaining and expanding the solid feature-set ATi introduced with it's RV670 tweak of the R600. Not quite a piece of cake, is it? To see how it was achieved, we're introducing the best (if you ignore the whole early-NDA lifting shenanigans) kept secret in recent GPU history, the Terascale graphics engine:

Terascale Graphics Engine

Terascale Graphics Engine

Designed to Perform

This is the part where we leave Kansas, Dorothy, as it actually becomes interesting and we can discuss the architecture. The big, and truly unexpected, bomb is the number of ALUs or, as ATi calls them, stream processing units. Most insider gurus were pegging the RV770 at 480 ALUs - which would've meant 6 SIMDs.  Well, that rumor can be laid to rest now: it's a 10 SIMD part.

Throughout the rest of this article, we'll be covering all of the bullet-points on that slide in detail. The last slide shows the general configuration of the 4850 we're having as a representative of the RV770 line so, whenever in doubt, check it out to see its specs again.