back to the issue of cooling

Bari Ari bari at onelabs.com
Thu Apr 24 12:57:20 EDT 2003


jbassett wrote:

>Transmeta quotes a TDP for their 1-Ghz Crusoe as 7.5 watts
>
>An Athlon XP at around twice the clock-speed is around 10* that at 75 watts
>
>but at .05$/kw*h I agree that it is unlikely that you could ever find an 
>operating cost that would be able to offset the greater cost and slower 
>performance of the Crusoe. But the density that you could pack them would be 
>incredible. If you were running so much cooler that less of a cooling system 
>investment were required that might change the equation.
>
>Or if there was ever a need for a highly mobile cluster system. You could pack 
>a great number into a single box and carry it about and perhaps because in 
>theory 10 Crusoes would dissipate the heat of a single Athlon you could easily 
>cool many of them. Joseph Bassett
>
>  
>
Density is not a problem using 75W Athlon's or Xeon's. You can stuff 
8-16 Athlon's or Xeon's into a 16.5" x 25" x 1.7" 1U box. Heat is 
transferred away from them (cpu, memory, chipset) using a combination of 
conduction cooling techniques and heat pipes in the case tied to a 
"heatbus" outside the case. The heatbus can be (depending on the heat 
generated) a large highly profiled heatsink requiring forced air 
convection, heat exchange coil (evaporator) or combination of the two.

What's more of a limiting factor in tightly packing cpu's is the 
distance required between cpu and chipset and also chipset to memory 
that eats up board space. There are very tight PCB routing rules that 
limit how closely devices can be spaced. 1" - 1.5" min. is common.

There's lots of talk about very dense systems but nobody ever really 
wants them. Everyone wants clusters with COTS motherboards and 
enclosures. They then rely on forced air cooling through slots in the 
enclosures and then cool the room air down with A/C.

--Bari Ari


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