But AMD surely didn't have working silicon samples for 5 years. There are multiple steps in developing a processor from ground up and each step (not stepping) can bring in its own bugs.
So if something is not working (who knows, maybe a feature B depending on feature A and A was not ready until stepping B1...), it may still be disabled and debugged->enabled with a later stepping. It's not about adding features (this is for Piledriver, Steamroller..), but about enabling only the working features. The transistors are there.
Do you remember that Hyperthreading is said to have already been included in Willamette but was not enabled before Northwood came?
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