[Beowulf] power usage, Intel 5160 vs. AMD 2216

Jim Lux James.P.Lux at jpl.nasa.gov
Thu Jul 12 23:56:14 EDT 2007


At 04:07 PM 7/12/2007, Mark Hahn wrote:
>>The 2GB dimms emit the same heat as the 1 GB dimms.  So if you have 
>>a 1000 node cluster, and you use the larger (slightly more 
>>expensive) 2GB dimms vs the 1GB dimms, you will emit somewhat less 
>>heat.  I haven't done the
>
>assuming the same number of chips per dimm.  if your 1G are single-sided,
>and 2G are double, you save nothing.  it's also interesting that for a given
>generation chip, the higher-clocked dimms are significantly hotter
>(say, 200 vs 300 mA max draw for 1G pc2/667 vs /800).
>
>also, I notice that x16 chips dissipate a lot more than x4 or x8, even
>though the chips have the same number of onchip banks.  I guess this 
>says that the main power issue is driving wide parallel buses at speed...

You betcha.. the power dissipation inside the chip is fairly low (on 
both ends of the path, either within the DRAM or within the CPU).. 
it's the drivers and receivers on the bus  (or just getting on and 
off chip) that consume the joules. Consider if you are using a 
voltage source and a series resistive termination that a well matched 
source will dissipate the same power as being transmitted (i.e. 
Thevenin).  In reality, the termination and the Z are partly 
reactive, which doens't theoretically use any power, but real systems 
do burn power charging and discharging the capacitance.



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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