http://www.anandtech.com/video/showdoc.aspx?i=2527
The 512-bit internal ring bus actually excites us the most; Cell's Elemental Interface Bus (EIB) uses a 16-byte wide quad ring bus, capable of transferring 16-bytes per cycle to the various SPEs. R520's ring bus would actually be four times wider than the bus found on Cell; though this implementation is in R520's memory controller rather than the PPE-to-SPE interface. With all the hype for R520 so far, everyone is banking on the memory controller to put X1800 ahead of G70.
http://www.hkepc.com/hwdb/r520firstlook-e.htm
As the card maker doesn't wish to reveal the R520 performance yet, but we can confirm that R520 at 24pp or 32pp will not be lower than that of the GeForce 7800GTX. Even though the 32pp and 24pp R520 mass production will face some difficulties, but the 16 pipelines R520 using the 90nm core will be clocked high to maintain a certain level of competitiveness. Apart from employing TSMC to make the 90nm R520 cores, UMC will be making them as well in the near future to make up the shortage problem and we can see more of the 32pp and 24pp R520 versions.
EDIT:......
http://www.anandtech.com/video/showdoc.aspx?i=2532
Pricing!
X1800 XT 16 600MHz 700MHz 512MB GDDR3 $599
X1800 XL 16 550MHz 625MHz 512MB GDDR3 $499
X1800 Pro 16 500MHz 500MHz 256MB GDDR3 $449
X1800 LE 12 450MHz 450MHZ 256MB GDDR3 $349
Common features to all R520 based boards include the new 90nm lead free manufacturing process, a Xilleon based TV encoder, SM3.0, H.264 decode acceleration and CrossFire support.