While Windows Phone 7 runs happily on ARM-architecture processors, suffice it to say that no traditional version of Windows has ever run on an ARM CPU.  But according to reports, Microsoft Corp. is preparing a full fledged ARM-based Windows in an attempt to capture tablet market share.

According to Bloomberg and The Wall Street Journal, Microsoft has reached an understanding with ARM Holdings Plc. and will announce the coming operating system at the 2011 Consumer Electronics Show, likely during CEO Steve Ballmer's keynote.

The shift seems a logical one.  For mobile applications, ARM is a particularly good fit.  It features much lower power consumption and similar clock speeds versus the rival x86 architecture.  While Intel has come a long way with its low voltage x86 Atom platform, it still lags behind ARM's designs in power efficiency.

In the long run, the announcement of an ARM-based Windows could spell very bad news for Intel, and to a lesser extent smaller competitor Advanced Micro Devices. 

The irony there is that Intel used to produce ARM CPUs, but in what now looks like an unwise move, it divested itself of those holdings.  After purchasing the Digital Equipment Company (DEC), Intel continued to design and produce the company's ARM-based "StrongARM" processors for mobile devices.  In 2000 it transitioned to a newly named line of ARM CPUs called XScale.  

But in 2006 it sold its XScale mobile processor unit to Marvell.  An XScale processor is found in the Blackberry Torch, among other devices.  To this day Intel and Marvell still co-own some XScale processor lines -- but only network processors, embedded processors and their ilk.  Intel firmly passed away its rights to mobile ARM designs -- a move it likely is now beginning to regret.

Furthering Intel's troubles has been its laggard pace at pushing out improvements to its Atom platform.  Microsoft had hoped to release Windows tablets this year, but delays to Intel's Windows-compatible Oak Trail (Atom) platform dashed those hopes. 

Currently the biggest ARM CPU makers are Qualcomm Inc., Texas Instruments Inc., Marvell Technology Group, and Samsung Electronics Co.

Robert Breza, a Minneapolis-based analyst for RBC Capital Markets, estimates that an ARM-powered Windows tablet would be as cheap as the iPad and could take 10 to 20 percent of an estimated 50 million unit tablet market last year.  But he says the company has to deliver, commenting, "They've got to come back with a product that’s better than 'me too' and is equal if not better in features.  A lot of tablets today are inferior to PCs."