AMD Opteron 856 socket: Socket 940

What the Opteron 856 is

The AMD Opteron 856 is a 3 GHz single-core server processor from April 2006. It runs one K8 core at 3 GHz with no turbo, so 1 core gives 1 thread. Cache is 1 MB of L2 on a 90 nm process. Power is rated at 92.6 W on Socket 940.

The 856 topped the Athens 800 series on a 1000 MT/s HyperTransport link. It exists because eight-processor servers wanted the fastest Athens single core with the full 1 MB cache for per-core licensed workloads.

Socket and motherboard compatibility

The 856 fits Socket 940 eight-processor server boards with a BIOS that lists Athens single cores. It suits multi-socket racks qualified for 92.6 W parts. Check the server maker CPU list for the exact board and stepping. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Memory, PCIe and cooling

Memory is registered DDR through the on-chip controller.

HyperTransport at 1000 MT/s links the CPU to the chipset and other sockets. PCIe slots hang off the chipset.

Cooling uses vendor qualified server heatsinks for the 92.6 W envelope with directed airflow.

Upgrade paths

On Socket 940 the upgrade is dual-core Italy or Egypt parts such as the 2.8 GHz 890 where the board lists them, or the 852 at 2.6 GHz for a lower cost single core. Beyond Socket 940 a move to Socket F needs new boards and DDR2 memory.