Although not so well known, nor commented, as the i7 or the Atom processors ARM are produced in larger volumes and brutally used in all types of devices, routers and ADSL modems to video games (such as the Nintendo DS) , cell phones and smartphones. Basically, the x86 processors are used in PCs, notebooks and netbooks, while the ARM are used in virtually all the rest.

Unlike the x86 processors, which are produced by Intel and AMD (and to a lesser volume also VIA), the ARM chips are not produced by one company, but licensed and produced by several manufacturers.

ARM Ltd., which is responsible for developing the chips and holder of rights in the architecture, produces processors, limited to license the projects affordable for other manufacturers who may choose different types of licenses, including options that modify the chips and add additional components. This is the case of manufacturers such as Qualcomm, Texas Instruments and Samsung, who develop their own solutions, including drivers and helpers several modifications.

ARM processors can be divided into two large families. The first is the chip ARM7, ARM9 and ARM11, which are older (although they are still the most used) and Cortex line, which represents the current generation.

ARM11 chips are used in most smartphones today (virtually all phones with Symbian orWindows Mobile released between 2007 and 2009), while the ARM9 and ARM7 are common in simpler devices and various electronic products. They are 32-bit processors very inexpensive and easy to program, which offers a great flexibility.

The Cortex family in turn is made for three different architectures. At the base of the pyramid have the Cortex A5, chips that are simple and low-power, intended to replace the ARM9 and ARM11 and various applications. Then we have the Cortex A8, which are more powerful chips, for smartphones and other mobile devices and the Cortex A9 multicore chips that are high performance. I spoke briefly on the Cortex A9 in the book of smartphones, then let the A8 and the A5, which will be used in much larger volumes.

The Cortex A8 is the mainstream chip inside the family. He is a dual-issue (two processing units), which processes instructions in order (like the Intel Atom) and includes an L1 cache of 64 KB, divided into two blocks of 32 KB (instruction and data). It also includes a large (in terms of a chip for embedded systems) L2 cache 256 KB, which can be expanded up to 1 MB in accordance with the level of performance desired by the manufacturer.

The Cortex A8 also incorporated a pipeline of 13 stages (compared to 8 stages of ARM11), which enables the use of operating frequencies much higher. The chips produced using a technique of 65 nm (as used in 3GS iPhone and Nokia N900) operate in the region of 600 MHz, but larger appliances (such as the smartbooks) as well as chips made using more advanced techniques are likely to operate at much higher frequencies, up to 1.0 GHz

In theory, an SOC-based A8 would have no problem to operate at around 1.5 GHz, the frequency at which performance would be competitive with Intel Atom, but it would result in much higher consumption is unacceptable for a smartphone or other handheld device .

The great advantage of Cortex A8 on the ARM11's performance. In addition to providing a clock performance by about 60% higher (up to 2 DMIPS per MHz), it can operate at higher frequencies, which makes the performance of most SOCs is at least twice that of previous generation chips. 
Roughly, we could compare the ARM11 with 486 (that processed one instruction per cycle and parked in their 100 MHz) with the Cortex A8 processor (that processed two instructions per cycle reached 200 MHz).

You can also draw a parallel with the Atom, which (being based on Pentium 1) also handles two instructions per cycle and also uses a relatively short pipeline (for an x86 processor), with 16 stages. The Atom is capable of operating at frequencies higher than the Cortex A8, but the performance per clock cycle is not very different.

The great thing is that Atom consumes nearly 5 times more energy than a Cortex A8 same clock. If we consider the total consumption of the platform (processor, chipset and other circuits support) Atom becomes even less competitive, since the chipset 945GSE/ICH7M theDiamondville platform is terribly inefficient.

An example of SOC based on the Cortex A8 is the TI OMAP 3430, which is used in the Nokia N900 and Palm Pre. He is a chip produced using a technique of 65 nm, which also includes a PowerVR SGX GPU 530, a video accelerator 2 + VAT and a chip ISP, along with all the usual interfaces:

The PowerVR SGX 530 is a relatively powerful 3D chipset, which includes a programmable unit for the processing of shaders, called GMI. Operating at 200 MHz, it offers a fill-rate of 250 megapixels, which is equivalent to almost half the processing power of a GeForce 6200, but with a ridiculously low power consumption.

He is a descendant of the Kyro II, which competed with the GeForce 2 MX at the beginning of the millennium and, as he makes use of tile-based rendering, to minimize the use of processing and textures, rendering only the visible polygons in each frame .

While the architecture has not had success in PCs (where it lost to the brute force of GPUs from nVidia and ATI), the Power SGX eventually found a good niche in mobile devices, where the high level of efficiency makes it possible to develop titles complex 3D graphics without compromising the autonomy of the batteries. A good example is the 3D games iPhone 3GS, which is also based on it:

Unlike PC games, using primarily the DirectX 9.0c, mobile 3D games are based on OpenGL ES 2.0. The two main reasons are the lack of a DirectX version for ARM processors and the simple fact that OpenGL allows you to create optimized code very well, resulting in better performance and better Battery life.

The Cortex A8 is also efficient video decoding. It can decode video encoded in H.264 VGA running at just 350 MHz in the case of the TI OMAP 3430 he is paired with a chip IVA 2 + accelerator, which is capable of decoding H.264 or MPEG4 at 720 × 480 and 25 to 30 fps (DVD quality), which not only allows you to watch non-HD videos without having to first convert them using your PC, but do so without compromising the autonomy of the batteries.

Thanks to the technique of manufacture of 65 nm, the Cortex A8 chips are more efficient than the old ARM11 (90 nm), requiring less energy to run the same volume of operations. The management system is also more energy efficient, making the power consumption when the processor is idle for only a few milliwatts, almost negligible.

The big problem is that with a faster system you tend to do more things (browse more pages, leaving more applications loaded in the background, etc.). Which means that eventually the total electricity consumption turns out to be larger. This explains the fact that many of the A8 based smartphones offer a range far from ideal, forcing the owner to recharge every night.

Then we have the Cortex A5, which is the baby of the family. As the numbering suggests, it is a low-cost and low power consumption, to replace the chips in the ARM9 and ARM11 devices easier. He can open doors for the creation of low-cost smartphones or handsets with much greater autonomy as well as being an option to use the Cortex A8 and A9 in smartbooks media players and low-end.

From the standpoint of architecture, it is basically a shortened version of the Cortex A8, which maintains the same instruction set, but adopts a simpler architecture, based on a single processing unit (single-issue), with a pipeline more short, only 8 stages. This change causes it to not be able to achieve clock frequencies as high, but in return is much smaller and offer a power consumption per cycle much lower.

Cortex A5 keeps the L1 cache 64 KB (two blocks of 32 KB for data and instructions), but abandons the use of L2 cache, since the performance gain does not offset the increase in chip size. Being a single-issue processor and with a short pipeline, the Cortex A5 is not as dependent on the cache as the two older brothers and the central idea of the architecture is just to keep things simple. Remember that the ARM9 and ARM11 processors also do not use L2 cache and that does not compromise performance.

Besides being produced in single-core versions, the A5 also supports the use of 2, 3 or 4 nuclei (the choice is up to the manufacturer), which makes it a strong option for multicore processor for smartphones, as it is less and more economical than the Cortex A9.

Produced using a technique of 40 nm each Cortex A5 occupies an area of only 0.9 mm ² (including the 64 KB L1 cache), which is less than 4% of the size of the Atom 45-nm (with its 25 mm ²). Even a quad-core version of the A5 would occupy only 6 mm ² (including additional support circuitry), which would still only a quarter of the area of Atom. A smaller area means processors cheaper and more space to include accelerators and various other components, resulting in more complete SOCs.

The Cortex A9 processors (and even the quad-core versions of the A5) provide a per-clock performance very competitive compared to Atom. However, there is a major barrier regarding the adoption of them in personal computers, which are the operating systems.

It is no secret that although Linux come slowly growing in volume of users over the years, the most used operating system on PC computers is Windows, which does not have a version for ARM processors. Microsoft offers only Windows Mobile, which is very limited and has a limited set of software.

Thus, almost all projects smartbooks, tablets and other devices based on ARM processors have been based on Linux, which has an ARM port quite complete. Two good examples are the Nokia tablets (N770, N800 and N810, with the N900, which turned smartphone), which are are based on Maemo and the various devices based on Android.

They offer good resources for web browsing, PDF readers, personal organizers, media players, games and other functions, but of course are not able to run AutoCAD or Photoshop (or even regular Linux distribution, compiled for x86 processors), the establishing a clear division between the ARM platform and PC platform and prevents a more direct competition between the two.

A manufacturer could create a mini-notebook or even a mini-laptop based on the Cortex A9 a quad-core, equip it with 1 GB of RAM and a 250 GB HD and a 15-inch LCD, but the fact the basis of completely different software would be very difficult to sell it.

Instead, manufacturers have chosen to use ARM chips in devices for web access (smartphones, smartbooks, etc.). And specialized devices such as Media Centers, attacking some areas that are covered by the PC, but without competing with them directly.

However, things may start to heat up if some company to develop a desktop operating system based on ARM Linux (as in the port of Ubuntu to ARM and maemo) that is accepted by the public, allowing companies to create "PC" based ARM processors and compete more openly with x86 processors