Reproducible builds like they are used for Bitcoin, Tor or the Debian package repository aim at making sure that the binaries you install exactly equate the source code that they are supposed to be compiled from. This way, one tries to make sure that the software does not have any backdoors that were silently inserted during the compilation process.
Can something like this be achieved for hardware components like motherboards and especially CPUs?
If one was to build a completely open piece of hardware (meaning that all the design documents are open and everybody could build it themselves from scratch if they had the needed tools, see RISC-V), would there be a way to "prove" or practically make sure that a given piece of hardware is exactly how the open documents describe it to be? Could you somehow verify that the component has not been tampered with during the manufacturing process?