[Beowulf] Re: Beowulf of bare motherboards

[Jack Wathey]

On Mon, 27 Sep 2004, Andrew Piskorski wrote:

>> http://www.abo.fi/~physcomp/cluster/celeron.html
>
> I recently bought a bunch of old ECS P4VXMS motherboards cheap on
> Ebay, in order to build my own personal home cluster for testing and
> experimentation.  I plan to mount them on metal shelves somewhat like
> the Celeron cluster shown above.  However, that raises the following
> questions:
>
> Normally, motherboards are mounted to the metal case using metal
> standoffs, which touch the motherboard ONLY at the designed mounting
> holes.  Is this in fact necessary?  Desirable?
>
> Is there any reason the standoffs need to be conductive?
>
> Would it be ok to instead simply screw the motherboard down to a flat
> piece of wood or plastic?  Or to wood or plastic strips which touch
> all along much of the bottom of the motherboard?
>

Andrew,

About a year ago I built a cluster much as you describe (bare motherboards 
on steel shelves), but with the motherboards mounted to aluminum sheets 
instead of wood or plastic.  I used nylon standoffs (Mouser electronics 
part #561-A0250; www.mouser.com), and everything worked fine.  The 
motherboards are properly grounded by virtue of the ground wires in the 
connector to the power supply, as are the aluminum sheets, but the 
standoffs are nonconducting.  The standoffs just snap into the aluminum 
sheets (which are 1/16 inch thick) and snap into the motherboard holes. 
There are no threads and no nuts involved.

Ken Chase (math at velocet.ca) has posted to this list, a year or 2 ago, 
about his experiments with packing motherboards close together in a 
plexiglas enclosure with no shielding between them.  I believe he 
concluded that this was a bad idea, because radio-frequency interference
between the boards caused some of them to fail to boot.  Also large 
quantities of wood or plastic near a motherboard is a bad idea because of 
the risk of fire.

Unfortunately I don't have a website describing my cluster, but, if you're 
interested, I could send you more details.  One final word of warning: 
building a cluster like this (bare motherboards in a customized enclosure) 
is LOT more work than you probably expect.  It was for me, anyway.   I 
didn't have much choice, because of space constraints, but you might give
serious thought to the more conventional approach.

Hope this helps,

Jack