[Beowulf] A Cluster of Motherboard.

Jim Lux James.P.Lux at jpl.nasa.gov
Thu Nov 10 05:35:03 PST 2005

At 08:43 PM 11/4/2005, oxylabtech at gmail.com wrote:
>  It would like to know if is possible to make a cluster of motherboards? 
> I don't speaking in a cluster of PC's, but of motherboards. Somebody 
> already saw? If it is possible, Could someone help me?

Sure it's possible.
Your problems are going to be power, cooling, and structures (assuming 
you're not in an environment where people care about electrical codes, RF 
interference, etc.)

Most mobos are designed to be installed by themeselves in a case with 
cooling running approximately across the board and with a fair amount of 
clearance above the board.  If you start stacking them close together, you 
might find it trickier to cool (although, with enough high power fans, 
anything is possible<grin>)

Power supplies might be another problem.  In a lot of computers, the power 
supply is bigger than the mobo, since the PSes are all designed to the 
standard ATX formfactor.  You "might" be able to run multiple boards off 
one power supply, but there are some traps for the unwary:
1) At low voltages (5V, 3.3V) and high currents (tens of Amp) there's going 
to be significant voltage drop in the wire between mobo and PS.  With just 
one mobo, that's taken care of by a sense wire.  With two, it's a bit more 

2) Sequencing and standby modes.  You'll have to figure something out.

3) Structural.  Eventually you'll have to change something.  It might seem 
elegant to just stack things on a long piece of threaded rod, but if you 
have to get to the board in the middle of the stack, you're in for a 
tedious project.

4) Grounding.  If you're hooking anything other than ethernet cables (which 
are galvanically isolated) to them, and you have multiple boards connected 
together by the ground planes (the threaded rod approach, for instance) you 
might have a problem with ground loops, because you'll have multiple return 

However, lots of people have successfully built clusters from stacks of 
mobos.  I think the biggest one (in terms of # of nodes) is the one with a 
dozen or so Via mini-ATX boards.  I don't know that I've seen any bare 
bones clusters with more than 20 nodes.  Probably because no "professional" 
user would ever trust such a thing, so you're left with a hobby cluster by 
an individual, and when you get to a cash outlay of thousands of dollars, 
things like allthread and cobbled together power supplies lose their appeal.

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James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875
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