I work in processor verification and my employer spends a great deal of money on it. Like "thechao" I am not allowed to talk about this, alas. A good place to look at some of what ARM do is:
CPUs are arguably the most crucial mechanical invention in history and yet the practical art of making them actually work right is shrouded in secrecy in service of greed.
On Windows/MacOS, the communication between the operating system and external devices (drivers) are completely shrouded in mystery. Theoretically the Nvidia graphics driver could be intercepting all your ethernet packets and sending them to the US government. (I have no evidence of such a attack, but it is theoretically possible) Drivers are extremely privileged, and are also a major gateway towards compromising computer systems)
If you don't think the GPU drivers are complex, then look at the perf difference between nouveau and the nvidia proprietary driver. Those guys are also working on the bleeding edge of optimization. Sure you could write a working driver in short order, but its not going to perform the same.
I'm not saying that they are not complex, that's why I chose them. But you have the source code for them, you don't have to write them from scratch. Some of the optimization techniques, even if not documented, can probably be studied from the change history. Of course, it will take a few years to grow new experts without knowledge passing from the old ones, but by and large the logic is there in the code.
From what I understand, the same can't be said of real microprocessor design - the complexities of aligning logical requirements with EE complexities, analog responses, and manufacturing process limitations are not at all captured in the 'code', not at the same level. We can hope that they are documented, at least to some extent, but we all know the general priority of internal documentation against other concerns, and the difficulty of documenting design processes.
