Let's see how the situation looks from above the battle field. Intel has a strong market share in its grasp thanks to a large number of products (processors, chipsets and so on) and a great marketing and advertising department. AMD on the other hand, is losing some market shares mainly because of a much more reduced product offering as it has no quad core processors to compete against Intel's Xeon.
All AMD can do for now is hope that the Barcelona core based processors it will soon launch will prove a real hit on both the server, desktop and mobile markets.
But not all is lost for AMD as its Opteron processor family still has some advantage over the Xeon. Or, at least in theory, it does. First, an Opteron processor is cheaper than its Intel counterpart, but this is only to be expected as AMD's Opteron is a dual core, while the Xeon is a fully fledged quad core processor. Secondly, it seems that the power needed by an Opteron is lower than the energy requirements of the quad cored Xeon and lower energy requirements usually directly translates into lower operating costs, more so when we talk about servers with as little as possible down time.
Idle Opteron-based server systems usually consume about 40 percent less power than servers equipped with Intel's Xeon Woodcrest processors do, but when the servers' workload increases and bigger demands are placed both on the processor themselves and on the memory systems, the energy consumption differences fade to almost nothing. It seems that the main reason of these power requirements differences is the type of memory each server uses as Intel uses FB-DIMM memory, while AMD's Opteron needs only vanilla DDR2 and FB-DIMMs are less capable of adjusting their power consumption to fit the needs of a given workload.
The FB-DIMMs are more performance centered than the DDR2 memory modules are, and they really provide a lot of it at high usage levels, the problem being that even at idle workloads, the power consumption is quite high but, on the bright side, its energy requirements do not get much higher if the workload increases. Plain DDR2 on the other hand doesn't consume nearly as much power at idle workloads do, and it is capable of scaling its power consumption in tone with the demands. Because of this, the power efficiency gap closes between FB-DIMMs and DDR2 as the servers' workload increases and the memory subsystem is more and more solicited. As a direct result of this, while Intel is the undisputed leader in terms of raw performance, computing power and CPU performance per watt, AMD's server platform centered on the Opteron processor and the DDR2 memory is better suited for systems with variable workloads and idle times in between. What this means is that Opeteron processors rate better than their Woodcrest counterparts when it comes down to measuring the power used in day to day activities.