PC Perspective compared the AMD Phenom versus Athlon X2. The Phenom is a pretty significant upgrade to the X2 series of processors, so take a look at how much of a difference there is between these products:

Considering the issues that AMD has recently had with their value based 780G chipsets on sub-$100 US boards, we can guess that they are even more gunshy about releasing higher TDP parts with the chance of a user buying a board which does not support 125 watt TDP and higher processors. While it is not AMD's fault that the motherboard manufacturers decided not to support the higher TDP parts with their budget boards, it is something that AMD nervously keeps its eyes on.

The difference between the older X2 and the new Phenom in per core performance is actually quite significant. AMD did a nice job in increasing performance without robbing the bank in terms of power consumption. The Phenom 2.3 GHz has about the same overall performance in single threaded applications as the 90 nm Athlon X2 3 GHz, and simply destroys it in multi-threaded performance, all the while pulling less power overall while doing it. AMD really is at the end of the line for squeezing more performance out of its 65 nm process, and it shows when attempting to clock the Phenom core past 2.6 GHz. Power consumption becomes unsustainable except for the highest end motherboards with a robust power delivery system.

The Phenom is keeping AMD competitive with Intel, but at a great price. The die sizes and yields of the Phenom are helping to keep AMD's margins low, all the while making their products less desirable from a power consumption standpoint when compared to Intels competing products. The Core 2 products are pretty amazing, and Intel certainly pulled out all stops when designing and delivering that product. All things considered, AMD did make a major step forward in terms of design and performance with the Phenom when compared to earlier products. We can expect more out of AMD in the near future, assuming that their 45 nm process pans out for them. The second generation Phenom should integrate more features, perform better per clock, and show some significant power consumption decreases over current Phenoms. This will also allow AMD to more adequately compete with Intel and their 45 nm products. Time will tell though.