Power Consumption and Conclusions
The Power Question

While AMD has modified their basic core architecture, as well as adding two more cores per die and a large L3 cache, what has it done to power consumption when compared to another 65 nm SOI design utilizing only two cores?  Well, that certainly is the big question, and the answer illuminates why AMD has not been able to release Phenom processors faster than 2.5 GHz.

AMD Phenom versus Athlon X2: Something Old, Something New... - Processors 17

Well, that certainly is interesting.  The Phenom 2.6 GHz model, at idle, is almost reaching the same power consumption as the 5000+ X2 at full load.  When looking at the 2.3 GHz Phenom vs. the 2.6 GHz version, we see a full 67 watts of power increase when the clockspeed is only increased by 300 MHz.  A 12% increase in clockspeed results in a 19% increase in power consumption.  The 2.3 GHz Phenom is rated by AMD at 95 watts, while the 2.6 GHz is not officially rated (cough- approximately 143 watts -cough) since it is not an official product.

We can safely assume that on AMD’s current 65 nm process, we will not see the Phenom go past 2.5 GHz.  Going to 2.6 GHz and above would simply result in a product with an insanely high TDP and very stiff requirements for motherboard manufacturers to support in terms of power delivery.  In the desktop market, this is simply unacceptable.  While AMD uses a system of constant improvement with their process technology, we are simply nearing the end of what AMD can do with its 65 nm process.  AMD will have to wait for their 45 nm process to increase the core clocks of the Phenom brand while still staying in the same 95 watt to 125 watt power envelope.  Luckily for consumers, AMD is further enhancing the Phenom core to make it more efficient in both power and performance when the 45 nm product is released sometime in late Q3 (we hope).

AMD Phenom versus Athlon X2: Something Old, Something New... - Processors 18

All tests were performed on the 790FX based Asus M3A32-MVP

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.

Conclusion

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.

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