Right after the Developer Preview was released, Microsoft had made it clear that Windows 8 on ARM will only run Metro and one of the main reasons might be battery life concerns.
Windows 8 On ARM TO Run Only Metro To Stay Competitive
A lot of users and developers have asked why Windows 8 on ARM won’t have support for desktop. With Windows 8’s dual nature, many were looking forward to having the best of both worlds on an ARM tablet. However, Microsoft won’t do that simply to remain competitive with other successful tablets; namely the iPad and its battery life efficiency.
As explained in a recent post about system memory usage, simply having extra RAM installed uses up battery life. Windows 8 developers have minimized the amount of runtime memory that the OS is using so that manufacturers are not forced to ship more memory.
The Competition Uses Less RAM
One of the main reasons why current tablets competing with the iPad have a really bad battery life is their 1GB RAM.
The fact is that the iPad ships with only 512MB of RAM, even on the 2011 iPad 2 model. And if Windows 8 were to run its full version on ARM, it would require twice as much memory. That would mean significantly less battery life. That would mean losing days on stand by mode.
So if Microsoft is to remain competitive, they have to make Windows 8 as efficient as possible. And taking the entire desktop part away was the logical choice. Since it won’t be of much use anyway on a tablet (it’s a mouse and keyboard based interface and the apps require powerful processing), it doesn’t need to be there. ARM is a mobile processor that is not designed to handle desktop class applications.
Some will say that Microsoft should have let the manufacturers decide whether they want to include it or not. The point here is that Microsoft has worked hard to ensure a seamless user experience that is standard across multiple devices. They would be wasting that effort if they go back and let the manufacturers choose what they want to ship — an underpowered desktop enabled tablet that needs frequent recharging or a speedy Metro only tablet that can effectively compete with the iPad. That would simply dilute the effect that Microsoft seeks to have with Windows 8.