Somewhere in Redmond (at least metaphorically speaking) are several very large piles of unsold Surface RT tablet components.
Why did the long-awaited and much-hyped ARM tablet running "Windows for ARM" Windows RT flop so badly, when ARM tablets running iOS for ARM from Apple are doing so well?
It's not just the Modern Windows - or Metro - interface. Yes, everyone hates it on desktop Windows (although we're all going to have to get used to it, for reasons I'll come back to in my next article). But on phones, it's actually quite well liked. Some customers even like Surface.
Everyone LOVES a tiled interface... on a smartphone
But Windows RT (which you can't call WinRT, which is - in typical Microsoft branding style - are confusingly different but related things) is not "Windows Phone 8 for tablets". It's not even compatible with Windows Phone apps - even though it's based on the same Windows NT kernel as Windows Phone 8.
The only operating system Surface will run is, yes, Windows RT, which is essentially Windows 8 for ARM – but a version of Windows 8 with much of its functionality disabled. Most desktop users dislike Windows 8's Start screen and its "Modern apps" – but on Windows RT, Modern apps are all you're allowed. Windows RT does have a desktop, but it's locked down - only Microsoft's browser Internet Explorer version 11 and the bundled version of Office RT (a version of Office Home and Student 2013) - can use it.
Similarly, Windows RT is entirely compatible with the standard Win32 API - so long as the app has been compiled for ARM, of course - but developers aren't allowed to use it. The marketdroids commanded that it be disabled. You're only allowed to install signed apps from the Windows Store.
It's possible to run standard Win 32 apps on a Surface RT that's been jailbroken. You can re-enable Win32 and then install and run a small assortment of FOSS desktop Windows apps that have been recompiled for ARM. But it's a hack, likely to disappear in future and it will probably go down about as well with resellers as rooting your smartphone.
Windows RT and Windows Phone... so close and yet so far
Something else Windows RT won't do is run Windows Phone apps, even though they're designed for an interface that looks just like Windows 8's Modern UI. Windows Phone 8 is a different branch of the family, more limited still than Windows RT, with severe compatibility restrictions.
And remember that mention of "the only operating system Surface will run"? That's a deliberate restriction, too. To get the case sticker (and marketing money) that says that their devices are compatible with Windows 8, PC manufacturers must use UEFI firmware instead of a legacy BIOS. A stipulation of this is SecureBoot, which means the firmware won't boot any code that isn't signed by Microsoft.
On x86 machines, you can turn off Secure Boot if you want to install Linux or some other operating system on your computer. But on ARM-powered Windows computers, you can't turn off SecureBoot, so no other operating system can be installed. No Ubuntu Mobile or Android (or WebOS, Tizen or Sailfish) for you.