The new Ati chipsets are aimed at supporting the upcoming 4x4 platforms (the next quad-core solutions from AMD the K8L).

The budget range will see the arrival of the RD550, a chipset that has been derived from the existing RD580 chipset that powers the current 1900 XTX series. The RD580 itself will continue to evolve and will be able to support three GPUs and two CPUs by the first half of next year.
The mid-range and high-end will see the arrival of the RD970, RD790 and RD740 chipsets, both of which will support the AM2 processors. The RD790 will be aimed at the enthusiast market, and will feature support for either 4 GPUs on 8X PCIe lanes or two GPUs on dual 16x Lanes. Nothing has been revealed yet about the RS790 or the RS740.