VAX 780 on eBay

Paul Koning paulkoning at
Sat Jan 1 13:33:19 CST 2022

> On Jan 1, 2022, at 2:21 PM, Grant Taylor via cctalk <cctalk at> wrote:
> On 1/1/22 12:17 PM, Dennis Boone via cctalk wrote:
>> IIRC nothing in the VAX cpu actually requires 3 phase.  The PDU(s) just eat that from the wall.
> I think that's the same with all the /computer/ equipment that I've seen which connects to 3ɸ power.  A single phase could be used for all of it.  But I'm told that it's simpler / more economical (from a wiring / cable plant point of view) to deliver more power to the equipment as 3ɸ than it is 1ɸ.

Largely true, but some disk drives (RP06?  RP04?) use 3-phase spindle motors.  And mainframes may use 3-phase power supplies; CDC 6000 mainframes do, though with those it's 3 phase 400 Hz produced by motor-generators (which in turn run off 3-phase mains power).


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