They Invented the Future

From the article: Xerox Parc’s Engineers on How They Invented the Future
Read the full article here: https://spectrum.ieee.org/xerox-parc

“I’ve always thought the fact that [David] Boggs was a ham radio operator was important…. [He] knew that you could communicate reliably through an unreliable medium. I’ve often wondered what would have happened if he hadn’t had that background.”
—Bert Sutherland

“I’ve always thought the fact that Boggs was a ham radio operator was important,” Sutherland said. “It had a great impact on the way the Ethernet was designed, because the Ethernet fundamentally doesn’t work reliably. It’s like citizens’ band radio, or any of the other kinds of radio communication, which are fundamentally not reliable in the way that we think of the telephone. Because you know it basically doesn’t work, you do all the defensive programming—the ‘say again, you were garbled’ protocols that were worked out for radio communication. And that makes the resulting network function extremely reliably.”

“Boggs was a ham and knew that you could communicate reliably through an unreliable medium. I’ve often wondered what would have happened if he hadn’t had that background,” Sutherland added.

Once the Ethernet was built, using it was fairly simple: a computer that wanted to send a message would wait and see whether the cable was clear. If it was, the machine would send the information in a packet prefaced with the address of its recipient. If two messages collided, the machines that sent them would each wait for a random interval before trying again.

One innovative use for the network had nothing to do with people sending messages to one another; it involved communication solely between machines. Because the dynamic memory chips were so unreliable in those days, the Alto also ran a memory check when it wasn’t doing anything else. Its response to finding a bad chip was remarkable: “It would send a message telling which Alto was bad, which slot had the bad board, and which row and column had the bad chips,” Thornburg said. “The reason I found out about this was that one day the repairman showed up and said, ‘Any time you’re ready to power down, I need to fix your Alto,’ and I didn’t even know anything was wrong.”

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