A Windows Central has been chatting to someone in Microsoft and thinks that Microsoft approached the company a few months back. The results are still unknown -- if the company has really made a bid to AMD.
It would be an interesting idea. Microsoft would save a billion dollars it pays every year to AMD.
Word on the street is that Redmond pays AMD $100 for every Xbox One SoC and if Microsoft uses similar chips for its Lumia smartphones, the savings could be much higher than this.
It would leave Sony having to pay Microsoft every time it wanted a chip for its PS4 console which would be a little annoying. It would could come up with a different technology from Intel, Arm or Nvidia and they would have to come up with a redesign.
Early it was suggested that Samsung is also interested in acquiring AMD, but there's no word from anyone about that idea.
As for the valuation, AMD's market capitalization rate is around $2 billion so it's not really difficult for Microsoft to shell out this much cash after all it has $93 billion in the bank.