Intel still enjoyed the upper hand, though, thanks to Dunnington -- its 7400 series of six-core Xeon processors.  These low power processors brought improved power performance and are built on a 45 nm process.  However, they were based on the Penryn architecture and thus lacked Nehalem's hyperthreading and DDR3 support, outstanding features of Intel's desktop Nehalem-based i7 processors.

Now AMD has moved to cut Intel's advantage, releasing a low power edition of its own six-core 45 nm processors.  Previous six-core Opterons (developed under the codename "Istanbul") have weighed in at 75 W for the ACP, while the new processors consume a mere 40 W.  TDP of the new processor is estimated to be approximately 65 W.  The processors beat Intel's Xeons in power consumption, while matching them in pure clock speed.  Processors clocked at 1.8 GHz (Opteron 2419 EE) are set to launch.

Pricing and availability of this new model has not been officially announced yet.

The Istanbul architecture does trail the Dunnington Xeons in pure memory speed, with an 800 MHz clock, versus memory speeds of up to 1066 MHz on Dunnington.  However, it makes up for this somewhat with its HyperTransport Assist technology and HyperTransport 3.0 technologies, which speed up data transfer from memory.

The processors are drop in replacements for the four-core Shanghai processors, released late last year.  The new six-core processors actually use less power than the four core processor, and improve per-watt performance by a reported 31 percent.  This helps ease the financial pain of upgrading, by negating the need to upgrade to a new power supply to add more processing cores.

AMD hints that more good things are in store.  AMD Server/Workstation Product Marketing Manager Andy Parma says that next year the company will unleash Lisbon six-core processors, which he says will feature architectural improvements, and even lower power consumption -- delivering six cores at less than 40 watts. 

Of course, these processors will feature tough competition from likely Nehalem-based Intel Xeons codenamed Gainestown which debuted earlier this year.  Eight-core (16 threaded) Xeons are also reportedly on the way and may be landing before the end of the year, albeit at likely a lofty price.  Expect Intel to price Dunnington processors competitively to counter the new Istanbul processors as well.