The new ATI Mobility Radeon HD 4000 series is derived from the RV770 architecture and resembles its desktop siblings, featuring up to 800 stream processors, support for GDDR5 and GDDR3 memory types, a 256-bit memory interface, and CrossFire support with the option to switch back and forth between discrete and integrated GPUs without rebooting.
Breaking down into the series we have the top end ATI Mobility Radeon HD 4850 and 4870, followed by the mid range HD 4670 and 4650 for mainstream systems, which has the same 320 stream units as the previous top-end units in the HD 3000 series but consumes less power. Lastly, the ATI Mobility Radeon HD 4500 and 4300 series will make their way into mainstream and ultraportable laptops with just 80 stream units to conserve energy and lower the price. All of the new parts will have support for Direct X 10.1 and support streaming 7.1-channel HD Audio through HDMI connections as well as HD playback all the way up to 1080p.
Systems from Asus, MSI and others will reportedly be available before the end of March. In fact, Asus announced new N81Vp and N51Tp laptops with Mobility Radeon HD 4600 GPUs a couple of days early, on Wednesday.