R600 refers to ATI's upcoming Direct X 10 (DX10) compatible graphics processing unit (GPU). Model numbers for the R600 series have not yet been released. The card is scheduled for a 1H 2007 release, with a Q1 release very likely.
Not a whole lot is known about the R600. As of this entry, no enthusiast site has received an engineering sample from ATI. So all specs are based on speculation and leaks from ATI. Based on ATI's new 80nm process, the R600 GPU is rumored to be clocked around 800Mhz. It will carry 512MB of GDDR4 memory clocked at 1.0Ghz (2Ghz DDR). The card is based on the PCI Express interface and will be Crossfire compatible. The R600 will also be the first ATI consumer card to have unified shader units (64 in total). Currently the only other GPU to have unified shaders is the Xbox 360's Xenos GPU, which was also designed by ATI. Another big rumored difference is the elimination of the "slave and master" hassle when using 2 cards in Crossfire mode. ATI has opted for an SLi'esque design with a communication bridge between the cards. This will also eliminate the need for DVI patch cables.
At this time no pricing information has been leaked or provided. Expect the R600 to cost at least $399