Understanding i5 GPU and switchable with ATI dedicated GPU?

[htwingnut]

I was curious about the i5 GPU with a dedicated ATI GPU. My understanding is that ATI has incorporated support for switchable graphics with the i5 GPU in their latest drivers. Is this true? Secondly, a laptop like the MSI GX640 does not offer switchable graphics which greatly reduces battery life.

What does it take to implement switchable graphics, and why wouldn't all laptops with an i5 GPU and ATI discrete GPU offer it? Is it expensive? What does it take?

 

[Winterpool]

This concerns nVidia graphics (and is an Apple solution), but it may give you some idea of what's possible:

Inside Apple's automatic graphics switching

Of course, there can be issues, eg unexpected / undesired switching. And unsurprisingly third-party utilities have been developed.