AMD Opteron 850 socket: Socket 940

What the Opteron 850 is

The AMD Opteron 850 is a 2.4 GHz single-core server processor from May 2004. It runs one K8 core at 2.4 GHz with no turbo, so 1 core gives 1 thread. Cache is 1 MB of L2 on a 130 nm process. Power is rated at 89 W in a Socket 940 package with part number OSA850CEP5AV in the CG stepping.

The 850 tops the SledgeHammer 800 series single-core stack at 1514 dollars in May 2004. It uses a 200 MHz clock with a 12x multiplier at 1.50 V and an 800 MHz HyperTransport link. The chip supports MMX, SSE, SSE2, Enhanced 3DNow, NX bit and AMD64 with registered PC3200 DDR. No higher single-core SledgeHammer 800 series part followed, so the 850 closed the 130 nm multi-socket line before Athens 90 nm parts arrived in December 2004.

Top-bin multi-socket status made the 850 the choice for flagship coherent systems. Eight 850 parts give eight cores at 19.2 GHz aggregate with 8 MB total L2, which suited large databases that scaled with socket count and per core speed together.

Socket and motherboard compatibility

The Opteron 850 fits Socket 940 multi-processor boards with registered DDR and SledgeHammer 800 series top-bin support. It needs a four- or eight-socket board qualified for 89 W operation. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Flagship coherent servers are the natural match. Boards listing 800 series parts at 89 W accept the 850 with matched cooling per socket. Power and thermal qualification matter most at the top bin, since all sockets run at peak current together.

Memory, PCIe and cooling

Memory is registered DDR with ECC per socket, reaching PC3200. Balanced populations across sockets give full coherent bandwidth. Server modules only.

HyperTransport at 800 MHz meshes sockets and the chipset, while expansion hangs off the chipset. No PCIe lanes originate on the die. Cooling uses top-bin 89 W heatsinks per socket with strong airflow. Filter and fan health decide stability at full load across many sockets. DDR2 needs later sockets.

Upgrade paths

On Socket 940 the 850 is the ceiling for SledgeHammer multi-socket single cores, so same generation upgrades stop here. Athens 850 successors on 90 nm with SSE3 offer a die shrink path where listed. Beyond Socket 940 a move to Socket G34 needs new boards. The 850 lifts with the lever, so swaps need no solder work.