Thanks for the link.
I'm somewhat familiar on why Intel would not include HRNG in their CPUs for many years. There are 3 sentences in the article about the reasons:
Those analog circuits are also a nuisance when it comes time to improve the manufacturing technology used to make the processor. Every few years, chipmakers modify their fabrication lines to produce integrated circuits at a finer scale, allowing them to pack more transistors into the same area. Making these shifts is pretty straightforward for CMOS digital circuitry, but each new generation of analog circuitry requires careful reevaluation and testing—a major headache.
Essentially even normal routine process improvements would prevent them from generating unbiased bits. This completely perverts their internal performance evaluations: either continue produce low-yielding chips with good randomness or improve yields and ship chips generating weak randomness.
The new generation system has sufficient bias-removal circuitry to properly self-test istself and fail with the machine check exception when the manufacturing gets improved too much.
