Re: Converting an existing 32-node PC cluster

From: Robert E A Harvey (robertharvey_at_my-deja.com)
Date: 08/18/04

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    Date: 18 Aug 2004 02:43:57 -0700

    "Rchapman" <rchapman5@earthlink.net> wrote in message news:<J_lUc.118$2L3.63@newsread3.news.atl.earthlink.net>...
    > "Robert E A Harvey" <robertharvey@my-deja.com> wrote in message
    > news:5acbdcbf.0408150901.78724770@posting.google.com...
    >
    > > 2. Fit 500W PSUs, and make a cable loom to parallel up all 4 mother
    > > boards. The 'sense' wires for the 5V and 3.3V rails can't be
    > > paralleled - either conenct them to just one mother board (in the
    > > middle) and use HUGE wire, or add 1K series resistors so they emasure
    > > the average on all 4 boards - and use HUGE wire. Diode-or the
    > > power-up requests from the mother boards to the PSUs.
    >
    > Do you have more information on making a 500W PSU supporting 4 motherboards?
    > Thanks!

    It was a guess - I have no idea what sort of mother boards you have or
    the consumption. you would need to do some sums. That's engineering.

    Have a look at page 35 of
    http://www.formfactors.org/developer%5Cspecs%5CATX12V%20PSDG2.01.pdf
    for the signal names.

    I have used an old 200W PSU to power 4 of the Epia M10000 mother
    boards with no bother at all. I made a custom wiring loom
    parallelling up everything except pins 13 and 16 and 20. I made sure
    all the looms were identical length, all made with 0.5mm sq wire, and
    connected pin 13 to just one of the mother boards. Bigger wire would
    be better, up to about 2.5, but then you need to make a break-out at
    the PSU end, as you won't get all 4 into a plug. Or you could cut the
    connector off the PSU and run the wires into something like a
    Weidmuler rail mounted terminal block.

    Pin 16 I connected to the anodes of 4 1N5001 diodes. The cathodes
    individually went to pins 16 on each of the mother boards. When you
    powered up one mother board by pressing the power request button, the
    others all come up. On power down you shut them down one at a time,
    and when the last one releases pin 16 the PSU goes off.

    I bought the connectors from www.farnell.co.uk. Farnell own Newark in
    the states, and have merged thier two catalogues.

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