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magic.shtml
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Erlkönig: magic.shtmlFrom "The Hacker's Dictionary", Guy Steele et. al. Some years ago I was snooping around in the cabinets that housed the MIT AI lab's PDP-10, and I noticed a little switch glued to the frame of one cabinet. It was obviously a homebrew job added by one of the lab's hardware hackers (no one knows who). The switch was labeled in a most unhelpful way. It had two positions, and scrawled in pencil on the metal switch body were the words "magic" and "more magic." The switch was in the "more magic" position. Closer examination revealed that the switch only had one wire running to it! The other end of the wire did disappear into the maze of wires inside the computer, but it's a basic fact of electricity that a switch can't do anything unless there are two wires connected to it. This switch had a wire connected on one side and no wire on its other side. Convinced by our reasoning that the switch was inoperative, we flipped it. The computer instantly crashed! A year later, I told this story to yet another hacker. He clearly doubted my sanity. To prove it to him, I showed him the very switch, still glued to the cabinet frame with only one wire connected to it. It was still in the "more magic" position. We scrutinized the switch and its lone connection and found that the other end of the wire, though connected to the computer wiring was connected to a ground pin. That made the switch doubly useless: not only was it electrically nonoperative, but it was connected to a place that couldn't affect anything anyway. So we flipped the switch. The computer promptly crashed. We still don't know how the switch crashed the machine. There is a theory that some circuit near the ground pin was marginal, and flipping the switch changed the electrical capacitance enough to upset the circuit as millionth-of-a-second pulses went through it. But we'll never know for sure. All we can really say is that the switch was magic. I still have that switch in my basement. Maybe I'm silly, but I usually keep it set on "more magic." - Guy Steele, "The Hacker's Dictionary" |