microprocessors

Obligatory link.

I think that it used to be fun to be a hardware architect. Anything that you invented would be amazing, and the laws of physics were actively trying to help you succeed. Your friend would say, “I wish that we could predict branches more accurately,” and you’d think, “maybe we can leverage three bits of state per branch to implement a simple saturating counter,” and you’d laugh and declare that such a stupid scheme would never work, but then you’d test it and it would be 94% accurate, and the branches would wake up the next morning and read their newspapers and the headlines would say OUR WORLD HAS BEEN SET ON FIRE. You’d give your buddy a high-five and go celebrate at the bar, and then you’d think, “I wonder if we can make branch predictors even more accurate,” and the next day you’d start XOR’ing the branch’s PC address with a shift register containing the branch’s recent branching history, because in those days, you could XOR anything with anything and get something useful, and you test the new branch predictor, and now you’re up to 96% accuracy, and the branches call you on the phone and say OK, WE GET IT, YOU DO NOT LIKE BRANCHES, but the phone call goes to your voicemail because you’re too busy driving the speed boats and wearing the monocles that you purchased after your promotion at work. You go to work hung-over, and you realize that, during a drunken conference call, you told your boss that your processor has 32 registers when it only has 8, but then you realize THAT YOU CAN TOTALLY LIE ABOUT THE NUMBER OF PHYSICAL REGISTERS, and you invent a crazy hardware mapping scheme from virtual registers to physical ones, and at this point, you start seducing the spouses of the compiler team, because it’s pretty clear that compilers are a thing of the past, and the next generation of processors will run English-level pseudocode directly. Of course, pride precedes the fall, and at some point, you realize that to implement aggressive out-of-order execution, you need to fit more transistors into the same die size, but then a material science guy pops out of a birthday cake and says YEAH WE CAN DO THAT, and by now, you’re touring with Aerosmith and throwing Matisse paintings from hotel room windows, because when you order two Matisse paintings from room service and you get three, that equation is going to be balanced. It all goes so well, and the party keeps getting better. When you retire in 2003, your face is wrinkled from all of the smiles, and even though you’ve been sued by several pedestrians who suddenly acquired rare paintings as hats, you go out on top, the master of your domain. You look at your son John, who just joined Intel, and you rest well at night, knowing that he can look forward to a pliant universe and an easy life.

Unfortunately for John, the branches made a pact with Satan and quantum mechanics during a midnight screening of “Weekend at Bernie’s II.”...