1. One of the links you posted (hexus.net) states that 5970 has 512bit ram bus. Others say its only 256. The truth is...?
That entirely depends on how you look at it. Its a board with 2 256-bit interface ASIC's, so combined bit-width is 512-bit and, the way it works, it providing bandwidth eqivelent of 512-bit.
2. Couldn't find any tests for resolutions larger than 2560. I do think Eyefinity should take a piece of "performance" and it's not correct to calculate FPS for 5760x1200 simply dividing FPS for 1920x1200 by 3. Or is it?
No, there's lots of things that affect perforance - more than just the number of pixels. For instance, a larger framebuffer (as a result of a larger "Eyefinity" resolution) may push data out of local RAM into system RAM affecting performance; also the FOV differnces may also mean that the amount of geometry processing going on is not 3x either, and with these being unified processors that also has effects on the amount of processing available for pixel shading.
Some have done some Eyefinity testing already, others looks to be following up later. Take a look here though:
http://www.pcper.com/article.php?aid=820&type=expert&pid=4
3. How can you explain a sneaky move lowering down the frequencies except power supplies? Just can't understand why did you do such kind of thing. You promised to make a killer card, and now you care about watts?
You know, it cost me a buck to get a setup ready for Eyefinity, its working now with 4870x2, but I want more than 18FPS and was waiting for 5870x2. I really have 750W power supply, but I would buy a 1000W if you told me it was the only way to make 5970 work.
The limitations itself could have been made for people like me with 750W I appreciate you taking care of me and giving me a chance to play right after I get 5970 without switching to 1000W, but do you guarantee that if I get 1000W and OC 5970 to 850/4800 the plastic won't cover my floor and there will be no crashes?
The PCI Express specification calls for a maximum provision of 300W for graphics, both HD 4870 X2 and HD 5970 max this specification out. With the Cypress GPU, though, we knew it would be require more power than RV770 becuase it was designed as a bigger chip; when designing the HF 5970 we had two options - keep within the specification and the standard infrastructure that exists (and tune the voltages and speeds accordingly) or break the infrascturcture and go beyond the specification. In the end we chose a hybrid - the default speeds are designed to fit within the spec and the default infrastucture, but we designed the board to facilitate higher current draws and allow users with higher quality power supplies to tweak the performance more. Can we guarantee OC specs? No, we can't, but we can say that the GPU's on those boards are screened to be high speed capable.
4. I can see that PCB layout hasn't changed a lot and it has the same parts at the same places as 4870x2. Will my Accelero cooler designed for 4870x2 fit 5970 or not?
Sorry I wouldn't know that, but bear in mind that the GPU positioning is not in the same alignment on the HD 5970 as it is the HD 4870 X2 though.