Windows Phone 8.1 Update Will Support Faster And Bigger Phones :

Microsoft is updating its Windows software for cellphones to accommodate larger devices and make it easier for motorists to reduce distractions while driving.
It's the third update to Windows Phone 8 software since the system's release a year ago. Devices with this update will start appearing in the coming weeks, and older phones will be eligible for a free upgrade, too.

Something that may appeal to motorists: a new Driving Mode will automatically silence incoming calls and texts so that you can focus on the road. You also can configure the feature to automatically send out a reply to say that you're driving.
When the latest Windows Phone 8 update hits devices at the end of the month, Microsoft's mobile operating system will get support for zippy quad-core processors and 1080p high-definition screens. That means Windows Phone devices will be able to sport five-inch, Apple iPhone-like retina-grade displays. It also means that we'll eventually see a Windows Phone phablet.

The push for bigger displays also means that more live tiles can fit on the screen, and big phones running Windows Phone 8 will be able to add an extra column of tiles to its home screen. The most universal change to Windows Phone 8 is that Microsoft has added a multitasking interface to the operating system for quick app switching.
 The free Windows Phone update will start popping up on the first devices sometime in the next few weeks