ExtremeTech has some more information about AMD's 4x4 dual-socket dual-core platform:
he 4x4 initiative will be directly targeted at enthusiasts, according to Moorhead. Each socket will include an AMD Athlon64 X2 chip in a new AM2 socket, although what limitations will be placed on the clock speed will not be released until a future date, he said. Each socket will be connected using AMD's "Direct Connect" architecture, which already provides a dedicated channel from each of the CPU cores out to the system memory, and to each other. Due to the nature of the Direct Connect architecture, each CPU can access the other's dedicated memory store.
"Whenever we add sockets, Direct Connect kicks in," Moorhead said. "It's a huge pickup in performance."
The 4x4 board will also tweak the front-side bus speed, according to Moorhead. The 4x4 architecture will use unbuffered, non-ECC DIMMs and AMD's "Pacifica" virtualization technology. "It's not a warmed-over workstation board," he said.
More info over here. This is one of AMD's ways to counter Intel's Conroe. However, I think the price and power consumption of such a system will be rather high.