AMD's new chipset consists of two chips: a North Bridge (incorporating the integrated graphics core and a controller of the graphics bus PCI Express x16 2.0) and a South Bridge.
AMD obviously did not intend the 890GX only as an integrated solution. As opposed to the 785G, the new chipset supports CrossFireX. Its PCI Express 2.0 x16 bus can be split up into two x8 buses, allowing to build top-performance graphics subsystems consisting of two graphics cards.
That's why the AMD 890GX should not be viewed as an ordinary integrated chipset for inexpensive and compact mainboards. It is instead positioned as a solution for mainstream systems, and most mainboard makers are going to install it onto their full-size and functionally rich products.
AMD is also planning to introduce a discrete chipset of the new generation called AMD 890FX. It will be accompanied with the same SB850 South Bridge and targeted at expensive computers. As opposed to the 890GX, it supports the most advanced CrossFireX implementation with two PCI Express 2.0 buses, each in x16 mode.
The AMD 890GX also boasts AMD's Dual Graphics technology. Its point is that the resources of the integrated Radeon HD 4290 core can be combined with the external graphics card to deliver higher overall performance. This technology works with the Radeon HD 5450 card, ensuring a 25% performance boost in 3D games.
Dual Graphics can be only interesting for users of entry-level graphics cards like the Radeon HD 5450, though. The more expensive Radeons have enough GPU resources of their own and won't have any performance benefits from the integrated graphics core due to the high overhead resulting from the interaction of the external and integrated GPUs.