11 Mar
2023
11 Mar
'23
1:20 a.m.
On 3/10/23 17:20, Bill Gunshannon via cctalk wrote:
On 3/10/2023 6:11 PM, Fred Cisin via cctalk wrote:
The VAX 11/780 was wired for 208 V 3-phase, but all the
internal power supplies ran line-line, so were single-phase.
Also, the cooling blowers had 208V single-phase motors.
The DECSystem 2020 (KL10B processor) ran directly off
3-phase power with a HUGE transformer in the bottom of the
cabinet.
On Fri, 10 Mar 2023, Kevin Anderson via cctalk
wrote:
Some PDP-11's although you can sometimes break them up and
just use
lots of 110/220 outlets. And then you get to watch the
lights in the house
dim when you fire them up.
Some Vaxen as well and some of those you cannot break up.
At least I never
figured out how. I always thought of the distinctions this way
(from my
basis of exposure from late 1970s through the 1980s) and
from a higher educational setting primarily:
Mainframe = repairs required multiple technicians, some
possibly there full-time; regular operator(s) present,
and a locked door located between you and the machine;
entire specialized room with raised flooring, extra-high
amperage specialized power sources and wiring, and
significant air conditioning
Minicomputer = Vendor still provides a technician (just
one) for repairs, who drives in out in a station wagon;
only a part-time operator only; an user can be located
in the same room; 240-volt wiring, but not particularly
outlandish
Microcomputer = Computer can sit on a desk or in a
"normal" room; broken computer taken by user to
someplace to be repaired or self-repaired; typically one
user, and only 120-volt household or office power needed.
Supercomputer = a really fast and specialized version
(primarily focusing on high-speed mathematical
computations) of a mainframe.
extension cord / dedicated circuit / dedicated pole
transformer
Which machines needed 3-phase? I would be willing to bet that the 1401, 360's and
4300
systems all required a bit
more than you get out of a standard 100AMP 220 volt
electrical feed.
And Univac 1100's didn't run on commercial power at all
but required a motor
generator between them and commercial power.
The IBM 360/50 and /65 used a "Converter Inverter" that
converted 208 V 3-phase utility power to single-phase 120 V
2500 Hz sine wave power.
All the logic supplies ran off that 2500-Hz power, and were
astonishingly small.
At least the mid-range 370's had built-in motor generators
that converted 208V 3-phase power to 120/200 V 415 Hz
3-phase power. The internal supplies ran off that, vastly
reducing the size of transformers and capacitors.
Jon