MadboxPC has posted a leaked presentation from AMD covering the upcoming RV670 cards and it looks like most of the already known details are in it. We're talking US$150-250 pricing and the Radeon HD 3850 and 3870 cards. There's also a slide that contains a Radeon HD 3870 X2 card and this could possibly be the product that has been known as the R670 or R680 depending on who you listen to.
There's a lot of information about the apparent advantage of DirectX 10.1 although time will tell how important these features really are. Energy consumption also seems to be important to AMD with the RV670 drawing some 50 percent or less power than the R600 or Radeon HD 2900 XT. There's also a lot of talk about AMD's PowerPlay technology and how it now can be adopted to draw less power even in-game.
There aren't a lot of benchmark figures, but the one graph that's on there puts the 3870 just in front of the 2900 XT. The 3850 is some 15 percent slower than the 2900 XT. The benchmarks were done on an Athlon 64 X2 6400+, 2GB of RAM and an RD790 board under Windows Vista 64-bit, so the results need to be taken with a bit of caution.
AMD will apparently enable overclocking when it comes to CrossFireX and more than two cards, which is interesting and there will even be an automatic option for this. It's not that strange though, as ATI/AMD has allowed for different speed cards to work in CrossFire as long as they belong to the same generation of GPU.
The two slides towards the end are quite interesting, as it seems like AMD hasn't quite made up its mind when it comes to clock speeds, although our guess is that the first one of the two is out of date, as it's listing availability as of November 1. If we can trust this information it looks like AMD has reduced the memory clock speed of the 3870 from 2.4GHz to 2.25GHz, while the 3850 has dropped from 1.8GHz to 1.66GHz.
You can find the full presentation here