This question is based on another question submitted here: Is it possible to make illegal clones of an Intel Core i7?
More specifically, it's based around this quote:
I've been led to believe it's something like a 60% yield (i.e. they produce 100 processors they only get 60 that actually work) and the rest have to be discarded.
I'm incredibly curious now. What's the usual yield like for AMD and Intel CPUs? Is this actually documented anywhere or is it something not often spoken about by either company? Are there any articles or external information AMD and Intel have released on the failure rate of the CPUs they produce?
Also, is there any documentation on exactly why AMD or Intel CPUs might fail during production? I understand today's CPUs are immensely complex beasts, but, given the environment they're manufactured in, is a 40% failure rate really that acceptable (assuming the poster's claim of a 40% failure rate is even accurate)?
Best Answer
Yield rates are definitely a commercial secret; they will likely vary from batch to batch with normal manufacturing variation and attempts to tune the process to increase yield.
Yield is inversely proportional to die size. The i7 die size for "Lynnfield" is 296 mm², according to wikipedia, which is pretty big.
Yield is also traditionally low on newer manufacturing processes. Intel are always on the cutting edge, as part of their "high performance / high cost" market strategy.
Spot failures are usually due to tiny imperfections in the silicon substrate crystal. There are also the usual alignment and patterning issues which may cause whole wafers to fail. Generally the whole thing is a very nasty process control problem; dopants and chemical reactions have to be applied completely evenly, again and again in each of the layers. A single tiny bubble will cause a failure.