Cray J932SE (was Re: Straight 8 up on Ebay just now)

Paul Koning paulkoning at
Wed Jul 20 07:59:50 CDT 2016

> On Jul 19, 2016, at 4:55 PM, Greg Stark <stark at> wrote:
> On Tue, Jul 19, 2016 at 5:47 PM, Mouse <mouse at> wrote:
>> For example, I once had a neighbour who replaced an outlet in his
>> kitchen.  Turned off the breaker, removed the old one, put in the new
>> one, all very nice.  Turned the breaker for that circuit back on and
>> popped the service main breaker.
> Heh, I knew what was coming here and that it must mean you were in
> Canada (and only then checked the sender...)
> But all this seems like a red herring. Surely the three-phase power
> requiring devices only require three phase for the cooling systems?
> Wouldn't it be easier to just use a modern switching power supply to
> provide 5V and feed cold air directly from your home hvac and not try
> to run 50-year old cooling and power?

Three phase power shows up in a bunch of places.  Some high current power supplies (pre switching era) use three phase input to increase the ripple frequency and reduce its amplitude, which significantly reduces the size of the required filter capacitors.  I remember that in the KL-10.  CDC 6000 mainframes go further, not only using 3 phase but also 400 Hz power for that reason (that also shrinks the transformers).

Cooling systems might run on 3 phase, or not.  The compressors in the 6000 series CPU cabinets are 3 phase motors.  But the DD60 display uses 3 phase power only for the high voltage power supplies; the cooling fans are run off 230 V 60 Hz single phase.

If I remember right, the RP04 uses 3 phase power for the spindle motor.  Probably not for the logic power, though.


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