News

Windows 8 on ARM Details Emerge

• By Kurt Mackie
• 02/10/2012

Microsoft on Thursday provided a lot of clarification about what to expect with Windows 8 on ARM, also known as "WOA."

In a 13-page "building Windows 8" blog post, Steven Sinofsky, president of the Windows and Windows Live Division, almost provided too much information. He addressed some WOA mysteries that have dragged on unanswered by Microsoft since its September Build developer conference. Some of the details were a little opaque, but Sinofsky also noted that the code isn't complete at this time.

With Windows 8, Microsoft added new client operating system support for the ARM platform on top of its traditional support for x86/x64 silicon, largely with an eye toward better addressing the mobile device markets. The company also had announced support a year ago in Windows 8 for new system-on-chip processors being developed by AMD and Intel.

More details likely will come when Microsoft releases the "consumer preview" of Windows 8 on February 29. In the meantime, here are some highlights from Sinofsky's detailed blog post.

There Will Be "Desktop Apps" on ARM
It now appears that WOA will have interface support for classic "desktop apps." This point had been an unsettled matter of public debate for about four months, although Microsoft's developer partners likely knew the answer. The issue has to do with Windows 8's radical design. The new OS has one Windows Runtime (WinRT) but two user interfaces. The desktop app interface is the familiar Windows 7-like experience where applications are displayed with chromed borders and mouse-driven "ribbon"-style menu systems. The new "Metro-style" app interface runs applications in full-screen mode, without chromed borders, and is optimized for touch interactions. Many speculated that Microsoft planned to eliminate the desktop app interface in WOA, but Sinofsky indicated it will be present and it won't cause any system-resource hits for Windows 8 users.

However, just because the desktop app interface will be present in WOA does not mean that old x86/x64-based apps will run on WOA devices. Those applications would still need to be reworked first by the developer to address the new WinRT. Sinofsky's statement on the matter was definitive.

"WOA does not support running, emulating, or porting existing x86/64 desktop apps," he wrote in the blog post.

For those individuals and organizations needing to run "legacy" x86/x64 apps on Windows 8, WOA isn't the right choice. Sinofsky directly addressed that issue in the blog.

"If you need to run existing x86/64 software, then you will be best served with Windows 8 on x86/64," he wrote. WOA conceptually should be considered to be the operating system to use for Metro-style apps, he emphasized.

There Won't Be Virtualization on ARM
Virtualization will not be possible on WOA machines. It will not be possible to run an application in a virtual machine on top of WOA.

"Previously we have detailed that WOA will not support any type of virtualization or emulation approach, and will not enable existing x86/64 applications to be ported or run," Sinofsky clarified in the blog post.

He further explained that WOA is packaged differently by component designers and hardware makers in comparison with Windows 8 on x86/x64. WOA is optimized toward achieving power savings on mobile devices, and Sinofsky contended that virtualization would run counter to this ARM approach.

"Virtualized or emulated software will consume system resources, including battery life and CPU, at unacceptable levels," Sinofsky explained. "Emulation and virtualization of existing x86/64 software also require the traditional PC environment of mouse and keyboard, which is not a good assumption for WOA PCs."

This latter contention is a little confusing because Microsoft had typically put out the message at Build that Windows 8 would have a touch interface, plus the option to use mouse, keyboard and stylus.

In contrast to WOA devices, Windows 8 devices running x86/x64 system-on-chip devices designed by AMD and Intel will have virtualization capabilities. Microsoft has said since its Build event that it will make its Hyper-V client available on the x86/x64 Windows 8 client operating system, enabling desktop virtualization.

Office "15" Will Run as a WOA Desktop App
Microsoft CEO Steve Ballmer had hinted at Microsoft's Build event that the company was considering devising Microsoft Office as a Metro-style application. That may still be happening. In the meantime, Microsoft has created an Office "15" (code name) solution, currently at technical preview stage, that will run on the new WinRT in Windows 8, but it will run as a desktop app.

"Within the Windows desktop, WOA includes desktop versions of the new Microsoft Word, Excel, PowerPoint, and OneNote, codenamed 'Office 15'," Sinofsky wrote in the blog post.

It's still not clear how Office 15 will be offered with Windows 8. Typically, Microsoft's hardware partners load trial versions of Office 2010 onto new Windows 7 PCs, which contain all of the Office bits. Those bits get unlocked when users choose to upgrade to the various Office 2010 editions.

Sinofsky stated that the Office 15 applications will be optimized for touch and saving power on devices. The ARM versions of Office 15 will have "fidelity with their new x86/64 counterparts," Sinofsky stated, noting that the ARM version of Office required "significant reworking of the product" by Microsoft.

WOA Won't Be Sold Like x86 PCs
Microsoft's goal is to ship PCs based on WOA "at the same time as new PCs designed for Windows 8 on x86/64." WOA will be a package deal based on ARM partner collaborations (Nvidia, Texas Instruments or Qualcomm), offering a different experience (except for the operating system's user interface) on every device, and the devices will come in multiple form factors. Furthermore, unlike an x86 PC, users won't have the option to install a new operating system to replace the one supplied by the manufacturer.

"End-users are technically restricted from installing a different OS (or OS version) on a device or extending the OS, so this is generally not possible, and rarely supported by the device maker," Sinofsky wrote in the blog. "Device makers work with ARM partners to create a device that is strictly paired with a specific set of software (and sometimes vice versa), and consumers purchase this complete package, which is then serviced and updated through a single pipeline."

Presumably, users would be able to upgrade the Windows 8 operating system on WOA devices, but that point wasn't made by Sinofsky. Those WOA device owners who may want to replace Windows 8 with a Linux-based OS won't be able to do that, based on what Sinofsky stated in the blog.

WOA Devices Won't Be Publicly Available on February 29
Sinofsky said that WOA is tied to specific hardware, which is custom made and expensive. Because of that circumstance, there won't be a way for the public to get their hands on a WOA device this month, even though the Windows 8 beta for x86/x64 devices will be released to the public on February 29 (Microsoft calls it a "customer preview" release). Sinofsky said that all of the WOA devices available have been distributed to Microsoft's hardware and software partners. Microsoft claims that the Windows 8 customer preview will run on hardware that was capable of running Windows 7.

Those wanting to test the Windows 8 customer preview by running it on a virtual machine may be able to do it, but Sinofsky downplayed that option. He commented that "although VMs are supported [on x86/x64 hardware], that is not the best way to try out the consumer experience."

Microsoft may issue its traditional "release candidate" and "release-to-manufacturing" versions of Windows 8 before the product reaches the "general availability" or release stage, but that point was not confirmed by a Microsoft spokesperson in response to an e-mailed question.

WOA will be different from x86/x64 Windows 8 in that there will be no "boxed" general release of WOA. Consumers only will be able to buy WOA preinstalled on the hardware. There won't be any separate WOA operating system product to purchase.

WOA users will get their consumer software and updates through the Windows Store and through Windows Update. The online Microsoft Windows Store sells Metro-style applications, both for ARM and x86/x64 devices. It's not clear whether an independent software vendor could sell a WOA app outside the Windows Store. The store functions as a sort of security check on WOA apps.

"Our focus on delivering a new level of security for consumers using WOA is paramount…. In fact, WOA only supports running code that has been distributed through Windows Update along with the full spectrum of Windows Store applications," Sinofsky explained in the blog post.

Sinofsky's blog post is well worth reading. I've omitted many details in this summary, such as developer and hardware considerations, which can be found in the post. He said that many of the features he described for ARM devices would also apply to AMD and Intel system-on-chip hardware.