Well so basically that's what I've been saying. I'm going to try this one to be my last post on the matter since it is way off-topic. And keep in mind that as always this is only my view, my opinion. Thoughtful and as based on evidence as posible, but just an opinion in the end.
Nvidia's only issue is that of over-promising and then under-delivering, due to both external and internal influences/problems. And yields have nothing to do on this, they do not have abnormally lower yields, looking at what evidences I could find.
What must be understood tho, if any conclusions are to be made from what is said in conference calls, is that in the GPU scene we have 2 players and it's very important to know who they are and in what situation they are.
AMD: Aside from the long standing situation that AMD has been living on for the past years, AMD lost the Apple deal that they had in previous generations and they have gained very few other OEM design wins. Not enough to make up the difference anyway. Their message is thus that of abundance. "We can meet demand" == "you can place orders". They want/need new customrs. Don't let the words make believe you that I'm saying this is the doom&gloom for AMD. They are just in a situation where they want more contracts, and their message reflects that.
Nvidia: Got Apple back and have more design wins than ever before. They are not able to meet demand for several reasons and thus their instance is that of keeping the customers and keeping them happy. And so "finding excuses" for underdelivering. Lack of wafer starts is THE reason as well as the fact they were not able to allocate enough of the available wafers, but both of these only translate to "cannot meet demand" and "not completely on their hands", as well as "the situation will hardly change in the near future". And that's not the message that Nvidia wants, so "yieds lower thn expected" is a good "excuse" considering the circumstances, because the promise of higher yields is always there for new nodes (not that it's false that yields are lower than expected, but neither is true the message that has been conveyed from this).
It does not mean anyone is lying, but everyone uses what is best for them. Wafer starts are very low, which is the innevitable truth and yields are lower than expected (which does not equate bad yields or yield issues). AMD is apparently able to meet demand which does not mean that they have good yields and plenty of wafer allocation. Devil is in the details.