What’s The Difference Between Windows 8 & Windows RT? [MakeUseOf Explains]

With the Surface tablet announcement a few weeks ago and the final release of Windows 8 looming ever closer, some people are understandably going to be confused about the various versions available.
I’m here to set the record straight; at least, on the differences between Windows 8, and Windows RT. Read on to find out about the various differences, as well as the pros and cons of each system.

Runs On Different Hardware

The primary difference between these two versions is the hardware it will run on. Nearly all PCs, and even newer Apple Macs, run on standardised x86 hardware, with a CPU from either Intel or AMD. Older Macs used a different PowerPC standard, but since switching over to Intel x86 chips, you’ve been able to run Windows on your Mac hardware too with either BootCamp or in a virtual machine. Windows software is currently all designed to run on x86 hardware.
However, you might be running a 64-bit version of Windows – this is actually still based on x86 standards though. x86 began as 16 bit, then 32 bit, and more recently 64 bit. All of it is still x86 though. You may see it sometimes refered to as “x86 vs x64“, but what they actually mean is “x86-32 or x86-64“.
Windows RT however is a special version of Windows 8; it’s designed to run not on traditional PC x86 hardware, but on the completely different ARM architecture. ARM chips are widely used in embedded systems; in fact, the iPad runs on a kind of ARM chip. Nintendo DS gaming consoles are also based on ARM CPU’s. These are the chips that will power the next generation of tablets, and these will run Windows RT.

Now you might be asking yourself whether software is compatible between the two systems, and that’s where things start to get difficult. That’s where Metro comes into play.

Metro

Metro is the new graphical interface that defines the Windows 8 experience. All versions of Windows 8, and Windows RT, will have Metro at their core. Apps made specifically for Metro will be able to run on any Windows 8 or Windows RT device, regardless of the hardware or chipset being used. Microsoft can do this because they’ve created a new set of programming APIs – the so called Common Language Runtime (CLR), which gives programmers access to the same set of system functions regardless of the precise hardware details. You write a Metro app, and it can run on ARM or x86 hardware – simple as that.
However, this doesn’t apply to any of your existing software. In time, a lot of it will be made available as a “Metro version”, but the software you have right now – all of it – is made such that it will only run on x86 hardware – your traditional PC. This software will therefore not be able to run on Windows RT. It will be compatible with Windows 8, so you’ll be able to continue using it if you upgrade your PC. But if you purchase a tablet that has Windows RT – despite the Metro interface looking identical on both devices – your existing software will not run.
If that was confusing, let’s summarise - Windows RT will not run your existing software. Windows 8 will.

The “Desktop”

Both Windows 8 and Windows RT have a Desktop mode.
Many people who have installed the Windows 8 preview are under the impression that the Metro interface is just an added layer on top of the existing regular Windows ‘desktop’, but this isn’t true. It’s more accurate to think of Desktop mode as just another Metro app, which you can use to browse the filesystem. So there will be a Desktop on both Windows 8 or RT.
In Windows 8 however, the Desktop mode ‘app’ is also used to run your existing (legacy) software. It provides the same functionality your Windows 7 or XP desktop had.

In Windows RT, you can only use the desktop to browse your files.
There is one exception to this I believe. If a Metro app wants to run on the desktop, so long as it has been programmed for Metro, it can run on the desktop on any device.

What About Office? Internet Explorer?

What would Windows be without Office? Here’s the deal – your copy of Office that you have now won’t run on Windows RT, because its a traditional x86 bit of software and we just established that legacy software won’t run. However, Microsoft is making a special version of Office that will run on RT, and they have confirmed that it will be pre-installed on at least the Microsoft branded Surface for Windows RT tablet. This cannot be guaranteed for other Windows RT tablets or devices, but at least the Surface does include it.

Internet Explorer is a contentious issue here though. On Windows 8, you can run whichever browser you like, whether that’s a Metro-optimized Internet Explorer, existing Firefox in desktop mode, or even a new Metro version of Firefox. You can install any browser you like , just as you always have been able to. On Windows RT though, Internet Explorer is all you’re getting. You cannot install a replacement browser on Windows RT.
This may change in time though; remember that Apple did a similar thing with Safari on iOS, and that’s now been opened up. This move may even be forced quicker than we expect thanks to anti-trust lawsuits; but for now, that’s the way it is.

Secure Boot

Windows 8 machines now include the option of running in secure boot mode. This prevents malicious boot code from running before the core Windows system has kicked in, and it also prevents you from installing Linux. We talked about this a while ago, but it’s up to the PC manufacturer to determine if secure boot can be disabled by the user; though we expect most manufacturers to enable secure boot by default, yet still allow the user to disable it, similar to how you might adjust BIOS settings now.

However, Windows RT systems don’t have this option. Secure boot cannot be disabled, so you cannot install a non-authorised operating system. This is much the same as an iPad, where you can only run iOS. Having said that, I thoroughly expect this secure boot method to be hacked within a few days of the first Windows RT tablets being released, but no guarantees. Put simply then, Windows RT devices will only run Windows RT.
I hope this has given a better overview of the differences between Windows RT and Windows 8. It’s probably just easiest if you think of Windows RT devices as being locked down like an iPad, unable to run your existing software and stuck with Internet Explorer as a browser. Windows 8 though – whatever your feelings on the Metro interface – can at least run all your existing software and be customized however you want.
Knowing all this, would you even consider buying a Windows RT tablet device, or will you be waiting for “proper” Windows 8 tablets?