Who's rewired their house for this hobby?

Jon Elson elson at pico-systems.com
Tue Nov 25 20:49:38 CST 2014

On 11/25/2014 03:02 PM, William Donzelli wrote:
>> 400Hz 3-phase power also helps.  That gives a ripple frequency of 2400Hz in
>> a fullwave "star" configuration, with only 13% ripple, no?  The same holds
>> for early model Cybers (even before they were called "Cyber") which used a
>> different variety of logic.
> Well, yes, of course. Which leads to the question why DEC did not go
> that route. I guess the KL10 power supply people were drunk (again).
IBM 360's used 2500 Hz single-phase power produced 
internally by a
converter-inverter unit.  it made the individual power 
supply modules QUITE
small.  The problem is they had totally minimal energy 
storage in the DC
link of the converter-inverter unit, so the machines were 
extremely sensitive to
the slightest power bobble on the incoming 208 V 3-phase 60 
Hz power.  The
SLIGHTEST flicker seen on a fluorescent light meant the 360 

The 370's went to 415 Hz provided by an internally-mounted 
set, this made the machines able to ride through significant 
power dropouts.

At least, the KL10B power supply DID work reliably.  Our 
university didn't
care about the power waste, but obviously it was a big 
problem for


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