AMD prototypes a Linux PDA. It's pretty clear why this is a good tactic - but I'll outline it anyways.
In platform markets, if you're not one of the platform coordinators, it pays to hedge your bets. The platform coordinators always and everywhere have the capability to appropriate most or all of the value from the platform, because they by definition control the platform via ownership of a critical resource (user base, IP, etc).
AMD is not only not a platform coordinator, but a rival to one of the platform coordinators. So the better it hedges it's bets, the less risk it faces. Not only that, but increases it's credibility and strength to make threats and other kinds of strategic moves - because it has walk-away option on the table.
Finally, this tactic is solid because it not only build on AMD's current resources, but also extends them for the future, letting us glimpse the beginnings of a future AMD value proposition which is both defensible and well differentiated.