One of the niceties of Microsoft’s upcoming Windows 8 operating system is that the number of “editions” of the OS has been reduced from six to four, with much of the consolidation coming at the consumer end of the spectrum. When considered in light of the traditional Windows desktop model, however, Windows 8 really only has three editions, with new entrant Windows RT rounding out the offering. Windows RT is the final name for what was commonly called “Windows for ARM,” Microsoft’s attempt to bring Windows to ARM-based processors commonly found in mobile devices.

Why ARM?

ARM Holdings, the company behind so-called “ARM CPUs,” has been around for decades, originally producing processors for low-power devices like networking equipment and consumer electronics. The design’s low power requirements and relatively open licensing of the technology quickly found ARM-based processors powering the world’s mobile phones. Companies like Qualcomm and NVidia developed “system on a chip” packages, where core components of a smartphone — like the CPU, video processing, and mobile network hardware — were contained on a single chip, further reducing power consumption.

Contrast this with Intel’s x86 design, common to traditional desktops and laptops, which was originally designed with little concern for power consumption or space savings. This rarely presented any challenges to Intel until the smartphone and tablet era took hold, leaving Intel in catch-up mode while ARM-based designs dominate tablets and smartphones, with Intel “inside” a grand total of three smartphones as of this writing.

While this is a simplified history and overview of the nuances between two very complicated computing platforms, the essential takeaway is that ARM currently dominates tablets and smartphones, and the two platforms are essentially incompatible. Even if you have a common operating system running on an ARM and Intel platform, you can’t take an application compiled for one platform and run it on the other. As we’ll discuss, this means you can’t run your existing x86-based Windows applications on Windows RT (with some exceptions).

What ARM means for Windows tablets

While Windows has a long history of running on tablet-style devices, they traditionally met with little success, primarily due to power. An iPad or Android tablet likely lasts an entire workday and appears to “turn on” instantly, since the device is effectively always powered up and only in a standby state — a computing trick that’s only possible if your platform is extremely miserly with its battery. Intel has struggled to match ARM platforms on the power front, but Microsoft has essentially opted to hedge its bets, creating a version of Windows for ARM-based platforms.

The application situation

Microsoft is betting that its upcoming Surface tablet presents a “hat trick” of sorts to enterprise IT leaders. It provides users with a familiar computing experience, it leverages the existing pool of Windows applications and Windows developers, and it fits nicely into organizations familiar with deploying, managing, and maintaining Windows. With ARM, the big question for CIOs should be around application support, since ARM trades the great power characteristics and associated size and weight advantages for what is presumably Windows’ biggest asset: its huge application pool.

While Microsoft has provided development tools that will allow newer “metro-style” applications to run on any version of Windows 8, existing Windows applications will likely not be supported on the ARM platform. Presumably the “big boys” like Oracle and SAP will quickly deliver tools that are universally compatible, but your niche and in-house applications will not run natively on Windows RT without recompiling, which is a potentially major undertaking.

Another interesting twist with Windows RT is that Microsoft will be including an ARM version of its Office suite with the operating system. This sweetens the deal for a good portion of your workforce who wants a lightweight computing device, and does little beyond jockeying spreadsheets and wading through a crowded Outlook inbox. If your average employee works in Office, accesses web-based applications, and perhaps connects to a handful of large-vendor systems, Windows RT looks fairly compelling. If you’re awash in in-house applications that haven’t been developed using the standard Windows framework or are beyond a few years old, you’re likely looking at a major overhaul if you want to go the Windows RT route.

Does Windows RT makes sense for your organization? What factors are you considering before signing on the dotted line with Microsoft’s latest push into the tablet space?