[Beowulf] precise synchronization of system clocks

Robert G. Brown rgb at phy.duke.edu
Thu Oct 2 10:41:24 EDT 2008


On Thu, 2 Oct 2008, Lux, James P wrote:

> If one considers that a single wire is about 1 uH/meter (typical electrical
> wiring will be much less, because it's a pair, with currents flowing
> opposite directions), the series L might be a few tens of uH.  At, say, 20
> A, there's just not much energy stored there.

I was thinking in terms of load on transformers, but yeah, I forgot
(again) that switching power supplies ain't got no transformers.
Voltage regulators and MAYBE UPS have transformers, but they also have
bloody damn big capacitors.  I'm just not used to a transformer-free
world.

Back in the very old days we had power problems in our server room (that
I think might have been connected to people using really big physics
apparatus in the building) and we bought a honker power conditioner to
run a subset of our systems.  If one set up a monitor within two meters
of the sucker, the CRT fuzzed and distorted -- the rapidly varying field
was strong enough to deflect electrons at two meters.  We kept it far
far away from our backup tapes...;-)

    rgb

-- 
Robert G. Brown                            Phone(cell): 1-919-280-8443
Duke University Physics Dept, Box 90305
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Web: http://www.phy.duke.edu/~rgb
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