Intel's 90 nm CMOS process was a disaster, at least in its variant for desktop or server CPUs, all of which had an unbelievably high leakage power consumption (the idle power consumption of a desktop could be more than a half of its peak power consumption).
On the other hand, AMD's 90 nm CMOS process has been excellent.
With its 65 nm process, Intel has recovered its technological leadership, but that was not the most important factor of success, because AMD's 65 nm process was also OK and it became available within a few months of Intel's process.
AMD has lost because they did not execute well the design process for their "Barcelona" new generation of CPUs (made also in 65 nm, like Core 2). While Intel has succeeded to deliver Core 2 even earlier than their normal cadence for new CPU generations, AMD has launched Barcelona only after several months of delays and even then it was buggy. The bugs required microcode workarounds that made Barcelona slow in comparison with Core 2, and that started the decline of AMD, after a few years of huge superiority over Intel.
