[Beowulf] powering up 18 motherboards

Alpay Kasal eno at dorsai.org
Thu Feb 17 21:43:00 PST 2005

James Lux, thanks for the extremely useful explanation. Btw, I'm in
Brooklyn, NY. 120volts, 60cycles, regular AC power. I don't know the gauge
of the wiring in the walls but (as mentioned in another response just now) I
suspect it is old wiring and is the reason for the strange 10amp circuit

I looked at the x10 modules. Seems like it could be very useful, just script
all of them from my headend. For now I'm going to try to handle the power-on
sequence myself. I figured I could steal 3 10amp circuits from the house.

Follow me... Turn on 4 nodes (on 1 strip) which will peak at 5.2amps. let
that settle down to a steady 3.48amps and hit another strip of 4 nodes.
Total draw while the 2nd batch is starting is 8.68amps. It should steady at
6.96. I then have room to turn 1 more node on. Then one more after that. A 4
step process to get 10 nodes powered up without going over 10amps. Perform
the same exact steps on a 2nd circuit. Annoying but possible without
spending anymore money.

I was really hoping a decent $200-300 UPS would come to the rescue here. Oh

I just had a thought... I planned on making use of wake-on-lan. I can just
start sending jobs to the whole network though if all of it is asleep, I'd
have to still be careful of the powerup-sequence. Grrrr. Maybe a script to
perform WOL before starting any number crunching.

Boy did I take nice big fat electrical lines for granted in the past!


-----Original Message-----
From: Jim Lux [mailto:James.P.Lux at jpl.nasa.gov] 
Sent: Thursday, February 17, 2005 7:18 PM
To: Dean Johnson; Alpay Kasal
Cc: beowulf at beowulf.org
Subject: Re: [SPAM] [Beowulf] powering up 18 motherboards

No, the UPS won't help.  It might make things worse, because as you flip on 
all that load, the voltage will sag, causing the UPS to turn on, which then 
might trip from the overcurrent (assuming you're not out buying a 2kW UPS).

You could use the X-10 type (aka Plug n Power) remote controlled relays 
(don't use Lamp modules.. you need Appliance modules, which are relays

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