winscape 2251
First what happened.
This was sometime during 1988, during a PM session a saturday (early morning ) where amongst others a dead ESMD (winchester; ISTR it was a CDC 496 MB, but I may misremember) was changed. It lived in a cabinet with seven siblings, 10 fans and a huge distrubuting power supply.
A new tech person was doing the service. We took the chance to do a full shutdown, a little nervous about what 2 hours without power would do.
Come power-up time the CPU etc came up fine, as did network controllers etc. But the disk racks just tripped the circuit breaker as soon as the console processor told the cabinets to apply power.
The tech person then forced the fuse up and reapplied power.
We heard a lound CACHUNK and then silence and darkness.
Not just in the computer hall, outside as well. We used to have an animated neon sign just opposite the computer hall. It was dark. The only light nearby was from the cars and trains.
Turns out the disks start up current had tripped our own breaker, the building breaker and the feeder station breakers. They did just what they were designed to do in the event of a such mbuttive short circuit.
The board shuffle discussed above, is what happens in the field. Debugging happens in a vendor lab. But many vendors of cheap peripherals may not have adequate lab facilities to do proper...
Explanation came later.
The tech needed to test the drive, so he had disabled power sequencing. Not just for the rack; it was the first rack in a chain of 4, so he disabled it for 28 drives. Ugh.
The power company was nice about it and had a tech person out in a matter of minutes. We managed to fix the fuses of our own premises ourselves, although the building one of hundred+ amps looked like a mess.
OTOH, that vaporised metal makes very nice coloured patterns on the walls.
-- mrr
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