Rasberry pi - high density

Lamar Owen lowen at pari.edu
Wed May 13 20:59:37 UTC 2015

On 05/11/2015 06:50 PM, Brandon Martin wrote:
> 8kW/rack is something it seems many a typical computing oriented 
> datacenter would be used to dealing with, no?  Formfactor within the 
> rack is just a little different which may complicate how you can 
> deliver the cooling - might need unusually forceful forced air or a 
> water/oil type heat exchanger for the oil immersion method being 
> discussed elsewhere in the thread.
> You still need giant wires and busses to move 800A worth of current. ...

This thread brings me back to 1985, what with talk of full immersion 
cooling (Fluorinert, anyone?) and hundreds of amps at 5VDC.... reminds 
me of the Cray-2, which dropped 150-200KW in 6 rack location units of 
space; 2 for the CPU itself, 2 for space, and 2 for the cooling 
waterfall [ https://en.wikipedia.org/wiki/File:Cray2.jpeg by referencing 
floor tile space occupied and taking 16 sq ft (four tiles) as one RLU 
].  Each 'stack' of the CPU pulled 2,200A at 5V [source: 
https://en.wikipedia.org/wiki/Cray-2#History ].  At those currents you 
use busbar, not wire.  Our low-voltage (120/208V three-phase) switchgear 
here uses 6,000A rated busbar, so it's readily available, if expensive.

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