actually I think they are worth over 12 billion now if I remember correctly, if not more, might be closer to 13-14 billion....
Current Nvidia market cap (i know, i know...) -> 17.11 B
Current AMD market cap -> 5.63 B
*In theory*, Nvidia could buy AMD largely with its own stock, but there are, as you know, a lot of obstacles after that.
The competition watchdogs all over the world would want to look closely at it first, delaying everything and creating investor uncertainties -dragging the stock value below desired levels which in turn would be bad news for the stock swap deal in the first place, making it instantly more expensive when effectively done-.
Then there would be a lot of trouble integrating engineering teams and projects (many of them working on very similar, but ultimately competing -and incompatible- products), patents would need to be sorted out, there would most likely be another wave of lay-offs (potentially hurting the new company remaining employee's morale), right when Intel is about to enter the fray of the "actual" real-time 3D graphics rendering market with Larrabee or something else.
Certainly not the best timing they could ask for...
Yet, i'm thinking more in the sense of if they wouldn't be interested in taking a minority stake in AMD, like that investment firm from Dubai's government did a few days ago.
That would guarantee first-look access to future CPU and HTT samples and patents, influence to a certain degree its board of directors and perhaps even enable broad joint project development in order to reduce R&D costs.
Even Intel teamed with IBM on Geneseo, and Sony teamed with Toshiba on Cell, despite their other aggressively competing business units.
Why couldn't Nvidia and AMD do the same now ? Just because the later bought a competitor of the former ?
That would be an emotional response, and the market does not condescend with such attitude when investors are loosing money...