Energy Efficient AMD Processors: Closer Look

In the beginning AMD was going to launch the Energy Efficient processor family including single-core and dual-core models for the quiet and economical systems only. These CPUs would be typically installed into multimedia home systems assembled with AMD Live! concept in mind that implies the acceptable noise level of 30dBA.

AMD announced energy efficient CPUs for Socket AM2 systems back in mid May. At that time they launched two processor families: with 35W and 65W maximum heat dissipation. This classification is still valid. Today the first group of the CPUs includes relatively powerful dual-core processors working at up to 2.4GHz frequencies and rated as 3800+, 4200+ and 4600+. These Energy Efficient processors dissipate about the same amount of heat as the Sempron CPUs, which makes them 37% more efficient from the “performance-per-watt” prospective than the regular Athlon 64 X2. The second group of processors is positioned as less high-performance but more economical solutions for Small Form-Factor systems and includes a single dual-core processor with 3800+ performance rating and a few less interesting for us single-core Athlon 64 and Sempron models.

Note that there is nothing extraordinary that Energy Efficient AMD processors appeared in the market. It is known that there is a linear dependence of the CPU heat dissipation on processor clock speed and squared dependence on CPU Vcore. These ratios help the processor developer to create more economical choices. The CPUs with 65W maximum heat dissipation work at slightly lower clock speeds and support lover Vcore of 1.2V-1.25V. This is exactly how they manage to reduce the thermal power of the dual-core processors from 85W to 65W. As for the dual-core Athlon 64 X2 3800+ with the maximum heat dissipation of 35W, it is the 1.075V Vcore and only 2.0GHz clock rate. In other words, Energy Efficient AMD processors are nothing completely new. The manufacturer simply sorts out at the packaging stage those semiconductor dies that can work stably at lower Vcore. After that they simply lower their core voltage and limit the maximum clock frequencies and voila! – you get the desired wattage.

Therefore, it means that you shouldn’t try to find any specific unique features in the Energy Efficient processors. From the microarchitecture and performance standpoints they are exactly the same as the regular processors. Moreover, they are manufactured with the same production technology that is used for standard CPUs. In fact, AMD Energy Efficient processors appeared solely thanks to the improved 90nm process used on Fab.30, which accommodates AMD’s major production capacities.

Keeping in mind that the maximum heat dissipation of the new Intel Core 2 Duo processors is 65W, AMD decided to get more aggressive about pushing its Energy Efficient solutions into the market. Of course, this is a very good marketing move especially since there are no technological obstacles that could prevent it from happening. With these actions in mind that company is already rearranging the major Athlon 64 X2 desktop processor family, so that it could logically contain both: the traditional Athlon 64 X2 alongside with their analogues with 65W TDP. These solutions may be regarded as Core 2 Duo alternatives not only from the price-to-performance prospective, but also from the “performance-per-watt” standpoint. Although AMD has set the prices on the new Energy Efficient solutions slightly higher, the users building quiet computer systems will hardly be scared away by that.

We are also getting ready for the arrival of the Energy Efficient processors with 65W and 35W maximum heat dissipation. First of all, let’s check out the marking differences. The processor TDP is indicated by the third letter in the OPN line and the third symbol in the processor marking respectively:

• “A” stands for “regular” heat dissipation and power consumption;
• “O” stands for Energy Efficient processors with the maximum heat dissipation of 65W;
• “D” stands for Energy Efficient processors with the maximum heat dissipation of 35W.

The formal characteristics of the dual-core Energy Efficient CPUs are the same as those of “regular” processors except the core voltage and heat dissipation section: