AMD began rolling out their revamped server chip lineup late last year with the introduction of 45nm Shanghai processors in November and, as promised, is now following up with low power versions. The company introduced five new High Efficiency variants, all quad-core, with speeds ranging from 2.1 to 2.3 gigahertz and rated at 55 watts using AMD’s own “Average CPU Power” scale. To put that into perspective, the first round of Shanghai parts had an ACP rating of 75 watts and a maximum clock speed of 2.7 gigahertz.

The company is pitching the new Opteron HE processors as a way for datacenter customers to “maximize performance during peak hours while managing the energy costs during idle and low-utilization hours.” Servers using the new processors are available immediately from HP and Rackable Systems, while Dell and Sun Microsystems are expected to have availability later in the first quarter.

In addition, the chipmaker has added a couple of 2.8GHz Opteron SE models to the Shanghai lineup. These chips have a higher 105 watt ACP rating and are aimed at high-performance data centers. Whether they are standard, HE, or SE parts, all of the Shanghai chips have 512 KB of L2 cache memory per core and 6MB of shared L3 cache. The chips also support 800MHz DDR2 main memory.