The most important design directive for Atom processors was to make a processing unit that packs some punch but is the most energy efficient x86 unit possible. Intel has taken the netbook market seriously enough to come up with these processors, and we all know that it’s quite a costly thing to make a new chip.

To make the best performance to power CPU, Intel had to come up with a few ingenious ways of cutting power usage. This limitation in power consumption led to a number of limitations in the technology itself, which I’d like to shed some light on.

1. Atom processors have a very limited L2 Cache, which directly correlates to arithmetic performance. These processors were not made for scientific calculations, so engineers elegantly threw the notion of a sizeable cache out the window.

Another problem with L2 cache is that it’s expensive to make. It takes up precious space on the processor die (surface of the core) and is made of the same transistors, but since it contributes less to real-life performance than it does to final cost, it was an area where they could simplify the chip.

A modern desktop processor comes with huge L2 to make sure the arithmetic unit is always busy. An i5-2400 for instance, has 6MB of this temporary storage, while a popular netbook core, the N550 has 1MB for two physical cores. Can’t be compared.

2. Memory interface. Netbooks, where atom processors are ment to be installed rarely have more than 2GB of system memory. In fact, these computers rarely have any use for more than that, so it was a straight-forward decision to simplify the controller interface, which is integrated right into the CPU.

As a comparison, i5-2400 can handle up to 32 GB memory. This limitation rarely causes problems, because the video chip runs out of juice much quicker than the RAM would in case you attempt at running a 3D game. I’d compare this to something James May said about the Bugatti Veyron. “At this speed we have fuel for fifty minutes, but that’s not a problem because tires will wear out in twelve.” or something along the lines.

An Atom processor is by far not a Veyron, but you can see the lack of point of installing more than 2 GB of operating memory.

3. Core frequency in the case of these units stays well under 2 GHz. The core itself could run at 2.2-2.3 GHz based on what’s possible at 45 nm litography, but it wouldn’t be a clock speed worth pursuing.

Any processor consumes more watts per hour the closer it gets to the limitations of the technology due to higher leakage current and internal temperature. (the higher the temperature, the worse a conductor becomes and the more current bleeds away into the insulator layer. The higher the clock speed is the more heat it generates.)

The most popular netbook Atoms are N450 and N550. They run at 1.66 GHz and 1.5 GHz respectively. Both processors are capable of running browsers and e-mail clients the way such an ultraportable notebook is supposed to.

4. Graphic performance is extremely limited in netbooks mainly because of Intel Atom processors and the lack of need for it. The graphic core is integrated into the processor in this case, which limits the performance of said element quite severely. Video capabilities have to reach a certain level to render high definition 2D picture, and that’s all they’re capable of doing.

This limitation of atom netbooks can be traced back to the main design directive, which states that nothing can be present in the processor that gives less than 1 per cent average performance for 1 per cent increase in power consumption.

5. Certain unnecessary instructions are left out of Atom processors on purpose. No one in their right mind would run virtual servers on an atom based computer, thus the lack of need for VT-x –which is a virtualisation technology in Intel processors–, for instance.

Think of Intel Atom processors as the bare minimum that can handle flash content and run a browser. Anything that’s not used by average desktop tasks is thrown out to save power.

Atom netbooks are usually not limited by their processor directly. Manufacturers could opt to install a dedicated video chip to circumnavigate limitations of the integrated graphics core for instance, but they don’t do that. These portable computers are limited by the fact that they’re made to be cheap on purpose.

At a certain price level, nothing remains to be excluded, which exactly what the case is with atom netbooks. They do what they’re designed to do and not a single bit more. Sorry people, no heavy gaming, but none of these interfere with your ability to use a netbook as a primary computer.