How the spectre and meltdown hacks really worked

We're Used to Thinking of computer processors as orderly machines that proceed from one simple instruction to the next with complete regularity. But the truth is, that for decades now, they've been doing their tasks out of order and just guessing at what should come next. They're very good at it, of course. So good in fact, that this ability, called speculative execution, has underpinned much of the improvement in computing power during the last 25 years or so. But on 3 January 2018, the world learned that this trick, which had done so much for modern computing, was now one of its greatest vulnerabilities.