Green IT -- Saving In The Wrong Area

A carefully-designed IPC with an Intel Core 2 Duo processor and intelligent features can put even an Intel Atom IPC to shame, not only with regard to energy efficiency but in terms of overall power consumption.

Intel Atom processors are designed to be a cost-effective and energy-saving alternative to multi-core processors. Indeed, a number of industrial PC manufacturers have also taken the Intel Atom on board. Yet a closer look at performance shows that the intelligent interplay of components is the truly vital factor in cost and energy efficiency.

Less is more

With this objective in mind, the R&D department at Intel got to work on developing newer and more economical processors. For more than two years now these processors have been on the market under the name Intel Atom. Not only notebook and netbook manufacturers are using them in their products, but also a number of IPC makers. The entire development was inspired by the lively debate around green IT. Processors were to be not only more energy efficient, but more cost effective as well. Intel took the approach of reducing the number of transistors in the chip. Fewer transistors would require less energy. The concept was based on a simple theory of minimizing the number of lossy switching operations. Fewer transistors would also require less chip space, which significantly increases the number of chips per wafer. Because the production costs for a wafer are more or less consistent, and independent of the number of chips, this creates a major cost advantage.

Fewer transistors have a direct impact on design. The Intel Atom functions based on "in-order-execution, "which means the processor handles the commands in a strict order. For example, to carry out a certain command, it has to wait for information from a comparably slower main memory. The processor isn't able to do anything else in the meantime. With only few exceptions, most current processors such as the AMD Phenom or the Intel Core 2 and Core i series use "out-of-order-execution". That means the processors can re-sort commands and, in the scenario mentioned above, use the wait time to handle other operations. This translates to significant performance improvements. The functional units for re-sorting commands and eliminating dependencies, however, are exceptionally complex and therefore require loads of additional transistors. These were left out of the Atom, which leads to the main disadvantage of the processor: marginal performance.

As a reference, the last Intel processor with in-order design before the Atom was the Pentium, introduced in 1993. Its successors, the Pentium Pro in 1995 and the Pentium II in 1997, had already been equipped with the higher-performance out-of-order design.

Reducing consumption by half

The amount of energy an industry PC uses is not determined by the processor alone. Components like the chip set, memory, hard drive, and especially the display, contribute greatly to that consumption. Reducing energy consumption for one component does not change the overall result by much. For example, if we reduce the energy consumption of a processor by 50% - a notable reduction indeed - from 5W to 2.5W, that translates to an improvement of just 8.5 percent for an assumed overall power consumption rating of 30W.

Diagram: Example distribution of consumption for an IPC with Intel Atom processor.

In order to get the entire computer to work in a more energy-efficient fashion, all of its components need to be designed for economy. That means that every component must be carefully selected and in sync with the other components. Yes, the Atom processor needs less actual power than other processors, but when combined with an energy-hungry chip set - which is often the case due to cost considerations - the savings don't add up to much at all. Installing an Intel Atom processor does not mean that the overall system will need less energy.

Practical tests

In order to back up these theories with facts, we tested two machines: an Industry PC from noax Technologies AG equipped with an Intel Core 2 Duo Mobile SL9400 processor with 2x1.86 GHz, and a standard Industry PC equipped with an Intel Atom Z350 with a 1.6-GHz processor, the embedded version of the Atom N270.

First a look at power consumption when the computer is idle. The IPC with Atom processor is already using 22W despite the fact that it has an economical US15W chip set - which also has extremely low-performance graphics. The noax IPC scores here with 19.2W despite the high-performance Core 2 Duo processors. This is due to the meticulous design and the active power management of the noax IPC, which deactivates or curtails unneeded components when it is idle. In this example, the brightness of the display is also automatically reduced, thereby saving even more energy. But even when the display is on full brightness the noax computer does not use more than the test machine.

A comparison of energy efficiency is worth carrying out. What is relevant here is not just the absolute energy consumption but, in particular, how much computing power you get for each unit of energy consumed. In order to do this we measured the machine's power consumption; computing power was determined using a benchmark. The result is the computing power per watt of power consumption.

The graphic shows one thing clearly: With 3.5 times the computing power per watt of power consumption, the noax IPC leaves the Atom computer standing still with regard to energy efficiency while delivering 5.5 times the overall computing power.

More performance

A carefully designed IPC with an Intel Core 2 Duo processor and intelligent features can put even an Intel Atom IPC to shame, not only with regard to energy efficiency but in terms of overall power consumption. The fact that performance is far higher is also something the noax IPC with multi-core processor was able to prove in impressive style.  Conclusion: An economical processor does not mean an economical IPC.

Mr. Engl – Development Director at noax Technologies AG: