17 Oct
2007
17 Oct
'07
9:22 a.m.
On 17 Oct 2007 at 10:18, Jochen Kunz wrote:
It was just the MG starting. The machine was switched
off. Current
droped to a few A once the MG got to speed. The MG has a big flywheel.
Therefore it needs all that energy to get up to speed. The idea is that
the flywheel stores enough energy to compensate short power outages. If
power stays off longer the disel kicks in. (But at Cray-Cyber they
skiped the disel. ENOSPACE.) AFAIK a minimal configuration of the
machine (CPU + I/O) needs about 20 kW.
One of the reasons that I don't really want one of the old 60's era
big iron mainframes (even if I could find one) is related to this.
CDC Sunnyvale did not have a backup power supply for their machines.
So, when power went, the automatic switch would switch over to--
nothing. When the onion fields in Moffet Park started giving way to
tilt-ups, power outages were frequent. When the lights went out and
that awful silence took possession of the machine floor, you packed
up your stuff and left. The CE's would probably be repairing the
dmanage to the machines for the rest of the day--and perhaps for the
next several days.
Power outages were not kind to big iron. Not at all. I remember
seeing an early mini and noticing that one could safely power it off
when not being used and I was amazed.
Cheers,
Chuck