Windows on ARM, Microsoft’s New Tablet Platform

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Microsoft Windows President Steven Sinofsky Presents Windows 8 at BUILD. Image courtesy Microsoft

Microsoft has good news for mobile users: the next version of Windows will indeed run full-sized desktop applications on low-power-optimized ARM-based tablets for use with a desktop and mouse. But Windows on ARM comes with caveats for users and developers. The only desktop applications approved to appear on ARM devices will be those built by Microsoft: Internet Explorer, Office, the desktop and file explorer, and other elements of Windows itself.

In an 8,600-word blog post published Thursday, Microsoft’s Steven Sinofsky, president of the Windows division, offers new information about how Windows on ARM, or “WOA,” devices will work. Sinofsky positions WOA as “a new member of the Windows family, much like Windows Server, Windows Embedded, or Windows Phone” — both like and unlike Windows 8 running on a traditional x86/64 desktop processor.
Some things work in the same way across both platforms, but others will be quite different.
While Windows 8 for x86/64 will be released in a public beta/consumer preview at the end of the month, WOA is still only being tested by developers on experimental trial devices. The two versions will be finalized “around the same time,” writes Sinofsky, but there’s no guarantee that they both will arrive on the same date.
“Our collective goal is for PC makers to ship them the same time as PCs designed for Windows 8 on x86/64,” Sinofsky writes. But considering that WOA demands much more significant integration of hardware and software, WOA devices themselves will almost certainly arrive some time later than new PCs running Windows 8 for x86/64.
“It is a good bet that the first devices will not be WOA,” IDC analyst Al Hilwa writes in an e-mail. “In fact, we may see Intel or AMD tablets before WOA tablets.”
In fact, overwhelmingly, Sinofsky does not refer to “Windows 8 for ARM” or “the WOA version of Windows 8,” but simply calls it “WOA.” “Windows 8,” meanwhile, is either referred to specifically as “Windows 8 for x86/64,” or context makes it clear that various “Windows 8″ references speak only to Windows running on x86/64.
In some ways, it’s been a mistake to say that Windows 8 will run on both Intel/AMD and ARM processors. Following Sinofsky’s post, it now appears more accurate to say there will be two new versions of Windows for PCs and tablets — one for Intel/AMD, and another for ARM.
Or, following Sinofsky’s metaphor of family relationships, if Windows Server is an older sibling and Windows Phone a first cousin, Windows 8 and WOA are fraternal twins.
A unified experience from “Start” to “Store”
Still, Microsoft’s goal is for most elements of Windows on ARM to be consistent with Windows 8 and earlier versions of Windows. “Using WOA ‘out of the box’ will feel just like using Windows 8 on x86/64,” Sinofsky writes. “You will sign in the same way. You will start and launch apps the same way. You will use the new Windows Store the same way.” And both versions of Windows will support the same range of peripherals.
The Windows Store element is important because it offers another major point of commonality among platforms. The only applications guaranteed to run on both Windows 8 and WOA will be “Metro-style apps” distributed and updated through the Windows Store.
But what about recompiling x86 desktop applications to run on ARM-based tablets? Sinofsky says no. “WOA does not support running, emulating, or porting existing x86/64 desktop apps,” he writes. It’s a sentence that developers of older software for Windows have anticipated for months. But it still must feel like a kick to the chest.
And what about sideloading applications, whether they’re new Metro apps or ports from x86? Again, no. “Consumers obtain all software, including device drivers, through the Windows Store and Microsoft Update or Windows Update,” Sinofsky adds.
Even running x86 or alternate applications in a virtual machine, Sinofsky later explains, would consume too many resources for WOA’s low-power-optimized devices. No virtualization of any kind is supported for WOA.
If we enabled the broad porting of existing code we would fail to deliver on our commitment to longer battery life, predictable performance, and especially a reliable experience over time… By avoiding these constructs, WOA can deliver on a new level of customer satisfaction: your WOA PC will continue to perform well over time as apps are isolated from the system and each other, and you will remain in control of what additional software is running on your behalf, all while letting the capabilities of diverse hardware shine through.
“If you need to run existing x86/64 software,” Sinofsky adds, “then you will be best served with Windows 8 on x86/64. If you’re already considering a non-Windows device, then we think WOA will be an even better alternative.”
Indeed, while you may log into WOA in a Windows-familiar fashion, this won’t be your father’s version of Windows. Forget installation discs and the .exe extension. Barbed-wire fences have come to the old prairie.
Microsoft applications for Windows on ARM
In terms of its own applications, Microsoft is offering two different kinds of continuity between Windows 8 and Windows on ARM. The first is a broad class of applications that will work on both platforms. The second is a small but important set of applications specifically developed by Microsoft for WOA machines that look and feel like traditional Windows desktop apps.
The first group is comprised of core “Metro style” apps (for our purposes here, read “Metro style” as “tablet”). These apps will support mail, calendaring, contacts, photos, storage and web browsing. These will work on both Windows 8 and WOA machines.
Here, the continuity runs from the tablet to the desktop. You can use the exact same apps on both devices, but will be limited to apps built and optimized primarily for use on tablets and other ARM machines. In short, you can take any app that runs on a WOA device and run it on a Windows 8 PC.
WOA machines, however, will not support “desktop” versions of these applications — i.e., versions whose look and feel are optimized for a keyboard and mouse and the traditional file-folder Windows visual style. This is the second group of apps, the second kind of continuity. And these apps will be Microsoft’s own.
Indeed, only a small number of core Microsoft applications and system utilities will support a “desktop mode.” Examples include:

• Windows Explorer, for copying or browsing files in the file system;
• running programs in the command shell;
• making system adjustements in the control panel;
• browsing the Internet and using HTML5 web applications (including hardware-accelerated versions) in Internet Explorer;
• and finally, Word, Excel, PowerPoint and OneNote in the new Office 15.

Parsing further, for these desktop-capable WOA applications, we can break them into two categories:

• on one hand, system utilities for power users that allow for greater control over their machines and the capability to peek behind the scenes of the OS;
• and on the other, franchise Microsoft applications that, while capable of being rewritten for touch, are really still most likely to be most valuable in situations where users have a mouse and keyboard.

Defining a standard experience on nonstandard devices
Note: Here I’m thankful to AllThingsD’s Ina Fried, whose “Highlights From Sinofsky’s 8,600-Word Opus” helped call some of these to my attention.

• “You don’t turn off a WOA PC.” Whoa. There’s no “sleep” or “hibernate” mode, either. Pressing the power button or allowing the device to shut itself off puts it in a low-power, quick-start state, where defined background processes continue to run. Microsoft calls this low-power state “Connected Standby.” It’s similar to what we’ve seen on mobile phones. (In fact, as Sinofsky notes, early builds of WOA were tested on phones, as they were the only ARM machines available.) But the new WOA model is quite different from anything we’ve seen on previous Windows PCs or are likely to see in Windows 8, which doesn’t offer the same kind of integrated power management. “For end-users,” Sinofsky adds, “a unique capability of WOA is that you are in control of what programs have access to background execution so that those apps are always connected, and information like new mail is always up to date.”
• PCs running WOA “will be built on unique and innovative hardware platforms provided by Nvidia, Qualcomm, and Texas Instruments.” That’s the big three in ARM silicon, and it’s just a fraction of the total ARM licensees. ARM manufacturers not participating in WOA development include Marvell, Sony and Samsung. Plus Intel and Apple — although you probably already guessed that.
• “Windows 8 will run on every Windows 7 logo PC.” But Windows On Arm clearly won’t. In fact, there will be no single master or vanilla version of WOA, nor will a version of WOA designed for one machine necessarily work on any other. “End-users are technically restricted from installing a different OS (or OS version) on a device or extending the OS,” Sinofsky writes, describing the very different ARM design and platform philosophy.

Microsoft doesn’t want to be the sole manufacturer of all WOA devices, like Apple is for iOS. But Microsoft also doesn’t want to cede as much control to device manufacturers as Google has with Android. So, just as with Windows Phone, Microsoft is trying to split the difference. It may have to tailor each version of WOA to individual devices, but by requiring that manufacturers standardize those devices to certain chassis specifications, it keeps that process manageable. Every version of WOA can be more or less identical, and every app in the Windows Store will work on every WOA machine.
But make no mistake, we’re not talking about phones here. This is the personal computer business. Even post-Ice Cream Sandwich, there really isn’t a rich, competitive operating system for tablets and cloudbooks just hanging out there for anyone to use. At least, not anything offering the range and scope of Windows.
Conclusions
In short, with Windows on ARM, Microsoft is asserting an unprecedented degree of control over a major computing platform — only Apple has tighter reigns on its software ecosystem. That’s a difficult comparison, though, because with iOS, Apple makes only a handful of devices, and manufacturers all of them itself.
Microsoft, meanwhile, supports a huge range of devices, and works with three chipset manufacturers and many more hardware partners, where it sets the standard for the hardware specifications of those devices, pushes them to be compatible with an even wider range of peripherals, and approves all of the software that can be installed on those devices.
Chips, chassis, applications and peripherals. Add the operating system, and that’s everything.
In return, Microsoft is promising greater security and reliability, plus an unusual degree of capability in a low-power, “post-PC” device. But the “no-compromise” machine also calls for compromises everywhere by the people who make and use it. That’s the bargain being struck by everyone involved, from silicon partners to end users.
By holding on to desktop compatibility and multiple OEMs, Microsoft may be clinging to a PC model that’s being overwhelmed in Apple and Google’s post-PC onslaught. Then again, maybe this is what the post-PC, post-Wintel world looks like. When Windows 8′s fraternal twin hits the market, we’ll have a chance to find out.