AMD Opteron 844 socket: Socket 940

What the Opteron 844 is

The AMD Opteron 844 is a 1.8 GHz single-core server processor from May 2004. It runs one K8 core at 1.8 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 82 W in a Socket 940 package with part number OSA844CEP5AV in the CG stepping.

The 844 continues the 800 series climb with flat power from the 1.6 GHz 842, using a 200 MHz clock with a 9x multiplier at 1.50 V and an 800 MHz HyperTransport link. AMD listed it at 698 dollars in May 2004, matching the 840 and 842 CG prices while adding clocks. The chip supports MMX, SSE, SSE2, Enhanced 3DNow, NX bit and AMD64 with registered PC3200 DDR. Early B3 revisions cost above 2000 dollars with PC2700 limits, so the CG revision cut price while lifting memory speed.

Flat pricing across 840 to 844 CG parts made clocks free within the power envelope. A multi-socket board qualified for the 840 at 82 W normally accepts the 844 with the same heatsinks, since only the multiplier rises. That drop-in lift made the 844 a common mid life upgrade for coherent clusters.

Socket and motherboard compatibility

The Opteron 844 fits Socket 940 multi-processor boards with registered DDR and SledgeHammer 800 series support. It needs a four- or eight-socket board with coherent links. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Coherent database clusters are the natural match. Boards listing 800 series parts accept the 844 with 82 W cooling per socket. Single-socket 144 and dual-socket 244 parts at the same 1.8 GHz do not scale beyond two sockets, so series must be matched to the chassis.

Memory, PCIe and cooling

Memory is registered DDR with ECC per socket, reaching PC3200. Each CPU needs DIMMs for balanced 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 matched 82 W heatsinks with strong airflow across all sockets. Uneven service leaves some sockets hotter, which hurts coherent performance. DDR2 needs later sockets.

Upgrade paths

On Socket 940 the steps are the Opteron 846 at 2.0 GHz and the 848 at 2.2 GHz for multi-socket boards at higher power. Athens 844 successors on 90 nm add SSE3 where listed. Beyond Socket 940 a move to Socket G34 needs new boards. The 844 lifts with the lever, so swaps need no solder work.