The complexity of x86-based systems has become so great that not even specialists can know everything. The recently discovered Meltdown/Spectre vulnerabilities, as well as numerous issues in Intel Management Engine, underscore the platform’s mindboggling intricacies. So, the chips manufacturer has to actively use of various means for manufacturing verification and post-silicon debugging.

https://www.blackhat.com/asia-19/briefings/schedule/index.html#intel-visa-through-the-rabbit-hole-13513