The AMD Opteron 156 was a server/workstation processor with 1 core, launched in May 2005. It is part of the Opteron lineup, using the Venus (E4) architecture with Socket 939. Opteron 156 has 1 MB of L2 cache and operates at 3 GHz. AMD is making the Opteron 156 on a 90 nm production node using 114 million transistors. The multiplier is locked on Opteron 156, which limits its overclocking potential.
With a TDP of 104 W, the Opteron 156 consumes a good deal of power, so decent cooling is needed. AMD's processor supports DDR1 memory with a dual-channel interface. The highest officially supported memory speed is 400 MT/s, but with overclocking (and the right memory modules) you can go even higher. Although neither the processor nor its chipsets support integrated graphics, certain motherboards include dedicated graphics chipset that can provide some basic display output functionality.
The SSE4 instruction set is not supported, which can cause problems with modern games, as they require that capability.