[Beowulf] Re: Cluster newbie, power recommendations (Geater at Home)

Ed Karns edkarns at firewirestuff.com
Tue Mar 21 08:15:26 PST 2006

On Mar 20, 2006, at 12:01 PM, beowulf-request at beowulf.org wrote:

> My greatest question, though, revolves around power distribution.   
> It seems kinda weak to simply use one PSU per motherboard,  
> especially if I take the time to devise a cabinet in which to  
> operate the goodies.  Is it possible to run maybe two or three  
> motherboards off a single power supply, given that the amount of  
> known power committed to run a mobo is light, compared to the total  
> workload of the average 350w PSU?

It is not advised to try to "plumb up" several motherboards together  
for operation from a single power supply. There is no real power  
saving advantage by doing this and it will only make for an  
unwieldily  mess. 1) You could easily "overload" an ISA power supply  
by trying to "parallel" the power leads, even if just to two  
motherboards ... 2) Power consumption is based on the actual load  
(the motherboard & drives), not power supply rating = a 350w PSU  
usually does not run at the maximum rating, but at the actual demand  
of the load (the motherboard & drives).

Your best bet: keep each motherboard in its own case with its own  
power supply. If you have a defective or non-operating power supply /  
motherboard / case, strip the RAM out and add it to other systems and  
keep the other good parts for spares. (You might also consider using  
the funds for you "special" cabinet to acquire more RAM.)

> This is a power-saving concept... if I could run 16 mobo's on 8 (or  
> even 6) power supplies, it might be more beneficial to my health  
> and well-being when the electric bill comes in.

... this is NOT! a power saving concept. The total power "consumed"  
will be done by the total number of system motherboards, plus RAM,  
plus drives, plus monitor(s) plus added accessories. In fact by  
"stressing" 8 power supplies to run 16 motherboards (and generating  
the extra heat), your total electric bill will actually go up, not down.

Ed Karns
(I have personally built more than 1000 ISA systems, plus quite a few  
of my own design.)

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