Is it time for open processors?

The disclosure of the Meltdown and Spectre vulnerabilities has brought a new level of attention to the security bugs that can lurk at the hardware level. Massive amounts of work have gone into improving the (still poor) security of our software, but all of that is in vain if the hardware gives away the game. The CPUs that we run in our systems are highly proprietary and have been shown to contain unpleasant surprises (the Intel management engine, for example). It is thus natural to wonder whether it is time to make a move to open-source hardware, much like we have done with our software. Such a move may well be possible, and it would certainly offer some benefits, but it would be no panacea.Given the complexity of modern CPUs and the fierceness of the market in which they are sold, it might be surprising to think that they could be developed in an open manner. But there are serious initiatives working in this area; the idea of an open CPU design is not pure fantasy. A quick look around turns up several efforts; the following list is necessarily incomplete.