1994-07-20-01.jpg Reading one of the PDP-11 handbooks, I think it was the Architecture Reference Manual, I stumbled upon a reference to coroutines. I remember the example they gave being pretty lame, and wondered where I could use it that it would really make sense.

In 1994 I got my answer. We had installed UPS equipment on our control computers, some PDPs and some VAXen, and that brought a bug to light that had been well hidden before, because power outages used to kill the whole machinery not just part. Now one of the slave PDP-11s would crash hard after a powerout on the DEA bus (Digital Eingang-Ausgang, also known as digital I/O, a separate module of special-purpose computers). A coroutine added to the DRV-11 driver (after dissassembling same) solved the problem.

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