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Microsoft Details Windows 8 for ARM

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Microsoft has detailed Windows 8 for ARM: architected for low power consumption, apps that can only target WinRT, restricted desktop that allows only Office 15 and some Windows components to run.

Microsoft demonstrated Windows running on ARM System-on-a-Chip (SoC) at CES 2011, and showed Windows 8 (Win8) for the first time at D9 Conference in Taipei, including running it on a prototype ARM machine. While there has been some rumors related to Microsoft’s true intentions regarding ARM, it was not clear if ARM will be considered an equal member of the PC family, whether legacy x86 applications will be able to run on ARM and if Win8/ARM will include the desktop interface besides Metro. Steven Sinofsky, President of the Windows and Windows Live Division at Microsoft, published a blog post offering clear details on their plans with ARM.

First of all, Sinofsky wanted to make sure this move won’t be seen as a departure from Intel/AMD architecture, but rather the opening up of new opportunities for Windows and its entire ecosystem:

We could not be more excited or supportive of the new products from Intel and AMD that will be part of Windows 8—across a full spectrum of PC form factors including tablet, notebook, Ultrabook™, all-in-one, desktop, and more that all take advantage of the new capabilities of Windows 8 while Windows 8 takes advantage of new features in hardware.

The new platform will be abbreviated WOA from Windows on ARM, being intended to be an equal member of the PC family along with x86 and 64-bit. Microsoft expects to see new WOA PCs shipped the same time when x86 PCs will be introduced along with the official Win8 launch. The ARM chips will be provided by NVIDIA, Qualcomm and Texas Instruments and will have a common architecture running the same set of binaries. WOA PCs will bring to customers a “no compromise experience”, offering the same user experience from sign-in to browsing the web with IE in hardware accelerated mode to using external devices as an Intel/AMD-based PC.

WOA PCs are engineered for lower power consumption. Such devices do no shutdown nor hibernate. When the power button is pressed, they enter in “Connected Standby” mode, and can remain there for weeks without charging. When the device is turned back on, it is fully on with all capabilities available. This feature has affected many WOA design decisions, especially backward compatibility with legacy Windows applications, according to Sinofsky.

WOA is to share a large code base with Win8, and the Windows Store will give them equal footing. All software, including device drivers, will be available only through the Store. Developers will be able to write apps for WOA using Visual Studio 11’s supported languages including C#/VB/XAML or JScript/HTML5 programming against WinRT, but they can also write native WinRT applications using C and C++. Code based only on WinRT will run both on WOA and x86.

WOA will partially support the desktop: “WOA supports the Windows desktop experience including File Explorer, Internet Explorer 10 for the desktop, and most other intrinsic Windows desktop features—which have been significantly architected for both touch and minimized power/resource consumption”. WOA will have a desktop version of Office 15 comprising of Microsoft Word, Excel, PowerPoint and OneNote, re-architected for a touch interface and lower power consumption, but Microsoft won’t provide any support for running, emulating or porting third party desktop applications to WOA. Emulation and virtualization are not supported because they “consume system resources, including battery life and CPU, at unacceptable levels”.

It is obvious that Microsoft allows a restricted desktop experience on WOA because there was not time to re-write Office and some of the Windows functionality for Metro. We could probably safely expect that all traces of the desktop will disappear from WOA in the future when Office will be fully “Metro”.

Unlike Win8 on x86, there won’t be plug-in support for the desktop browser in WOA, according to AllThingsD: “Sinofsky also said that the version of Internet Explorer for Windows on ARM won’t support plugins such as Adobe Flash, noting the trend in the industry away from supporting Flash on mobile devices.”

WOA will be available only with new devices, and not sold separately.

Sinofsky reiterated Microsoft’s intention to provide a Windows 8 Consumer Preview edition available to all by the end of February when a limited number of WOA PCs will be made available to invited developers and hardware partners for testing purposes.

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