AMD Opteron 840 socket: Socket 940

What the Opteron 840 is

The AMD Opteron 840 is a 1.4 GHz single-core server processor from May 2004. It runs one K8 core at 1.4 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 82 W in a Socket 940 package with part number OSA840CEP5AV in the CG stepping.

The 840 opens the 800 series SledgeHammer line for four- and eight-processor servers, where the leading 8 marks multi-processor use. It shares clocks and cache with the 140 and 240 at 1.4 GHz, yet the 800 series package enables coherent links across four or more sockets. The part uses a 200 MHz clock with a 7x multiplier at 1.50 V and an 800 MHz HyperTransport link. AMD listed it at 698 dollars in May 2004. The chip supports MMX, SSE, SSE2, Enhanced 3DNow, NX bit and AMD64 with registered PC3200 DDR on CG parts.

Multi-socket scale defines the 840. Four 840 parts give four cores per chassis with shared memory coherence, which suited mid range database clusters that needed socket count more than per core speed. That scale is why 800 series parts cost more than 100 and 200 series parts at identical clocks.

Socket and motherboard compatibility

The Opteron 840 fits Socket 940 multi-processor server boards with four or more sockets, registered DDR memory and SledgeHammer 800 series BIOS support. It needs a multi-socket board with coherent links, not a single- or dual-socket board. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Four- and eight-socket rack servers are the natural match. Boards listing 800 series SledgeHammer parts accept the 840 with matched 82 W cooling per socket. Single- and dual-socket boards need 100 and 200 series parts instead, even though clocks match. Unlisted multi-socket boards may boot with only a subset of sockets active.

Memory, PCIe and cooling

Memory is registered DDR with ECC per socket, reaching PC3200 on CG parts. Each CPU needs its own DIMMs for balanced bandwidth across the coherent fabric. Only server modules boot.

HyperTransport at 800 MHz links all CPUs to each other and to the chipset in a coherent mesh, while expansion hangs off the chipset. No PCIe lanes originate on the die. Cooling uses matched 82 W server heatsinks per socket with strong chassis airflow. All sockets need equal cooling and paste for stable multi-processor operation. DDR2 needs Socket G34 successors with new boards.

Upgrade paths

On Socket 940 the steps are the Opteron 842 at 1.6 GHz and the 844 at 1.8 GHz with the same multi-socket scope. The 840 EE at 30 W suits dense multi-socket racks trading clocks for power. Athens 800 series successors on 90 nm add SSE3 where listed. Beyond Socket 940 multi-socket growth needs Socket G34 with new boards. The 840 lifts with the lever, so swaps need no solder work.