During Microsoft's presentation of Windows 8, a handful of the company's hardware partners showed off tablets and notebooks running the OS, some also featuring Microsoft Office. But if you looked closely, you would've noticed that missing from the equation were Intel and AMD, replaced instead by ARM chips made by rival ARM Holdings.

ARM chips are used in 99 percent of the world's cellphones, tablets, and other mobile devices, where they're favored for their miniscule power consumption. However, there are rumors that Apple might switch to ARM for its notebook range, and, in a shock announcement at the beginning of this year, Microsoft announced it was porting Windows 8 to ARM chips in a bid to unify the desktop and mobile versions of the operating system.

This is less shocking than it sounds, and Windows hasn't always been exclusively x86. Windows NT was created to be portable so it would run on DEC Alpha, PowerPC and MIPS chips just as well as it did on x86 (and NT went on to be the basis for XP). However, this move was aimed at the high-end workstation market. Adding in ARM support is the first time Microsoft has used anything but x86 for consumer-oriented Windows devices.

Intel may well be feeling jilted, despite the fact x86 remains the primary focus for Microsoft's desktop products. But there's still a nagging question: What are the benefits of an ARM computer when they go on sale next year, compared to similar offerings from Intel and AMD?

PROS

Long battery life: ARM chips are designed to use as little juice as possible. The Apple iPad is powered by an ARM chip, for example, and lasts about 10 hours. The chances are that ARM chips available when Windows 8 is launched next year will be even more frugal. Intel and AMD have mobile offerings in their Atom and Fusion ranges but, in terms of power requirements, they are gas-guzzling Hummers to the ARM's Prius. x86 simply isn't designed to provide the ultra-low-power platform required by today's mobile devices.

Lower prices: Intel and AMD control most of the x86 market, giving manufacturers little realistic choice when it comes to processors (and Intel holds most of the consumer mindshare). In contrast, the company behind ARM doesn't actually make chips itself. Instead, it creates reference designs that are licensed to manufacturers. Thus, there are many companies producing ARM chips, such as Texas Instruments and Nvidia, and all are fighting for customers. Chip prices are extremely competitive, and those savings can be passed on to consumers, especially in a marketplace where ARM devices are competing directly with more expensive Intel and AMD offerings.

Fewer viruses: ARM and x86 are completely different computing architectures. It's not yet clear whether Microsoft will provide a compatibility layer that lets users run older x86 software on the ARM version of Windows, but it's a technically difficult task. Instead, users may need to have software compatible with the ARM versions of Windows. The result? ARM users will be guarded against malware targeting x86 Windows. That's not to say cybercriminals won't start creating ARM-based malware. But an ARM computer will be immune to the hundreds of thousands of viruses that currently target Windows.

CONS

Poor performance: Low power consumption comes at a price. An Intel x86 chip will be a lot faster in real-life tasks than an ARM chip running at the same clock speed. Although ARM chips get faster on each release -- the top-of-the-line ARM Cortex A-15 design can run up to 2.5GHz across multiple cores -- there simply isn't the need for speed that drives Intel and AMD designs. On the other hand, there are many who argue computers are plenty fast enough nowadays for everyday tasks. It's only gamers who might miss the out-and-out performance.

Gaming won't be great: ARM chips are based on a System-on-a-Chip (SoC) design. They aren't pure CPU silicon, like most Intel or AMD x86 chips. Often ARM processors integrate 3D graphics -- Nvidia's Tegra 2 chip incorporates the GeForce GPU, for example -- but these are many generations behind the latest discrete graphics cards for PCs. In other words, 3D gaming is possible but don't expect LA Noire levels of realism just yet. However, all the signs are that mobile gaming prefers a simpler approach compared to desktop counterparts -- consider Angry Birds, for example.

Not 64-bit: All ARM chips are currently 32-bit and ARM has yet to release a 64-bit design. In theory this limits ARM computers to just 4GB of RAM, but in up-coming ARM chips this limitation will be bypassed by including a 40-bit memory controller that allows ARM computers to access up to a terabyte of memory --enough for the next 5 to 10 years, at least

source:http://www.pcworld.com/article/229241/windows_8_and_the_arm_revolution_the_pros_and_cons.html#tk.mod_stln