[Beowulf] 90nm opteron power usage

[Mark Hahn]

> Anyone know how much the memory could contribute to the overall power load?

fairly minor: I just looked at a micron 512MB dimm that had a 
peak draw of ~8.5A at 2.6V -> 22W.  that's for a dimm with the max
number of chips, operating bank interleaved, one read per cycle.
a real system could never manage that.  a same-spec device with 
half the number of chips dissipates half the power, and a more 
realistic full-load dissipation is more like 2A -> 5W.

so figuring ~30W of memory in a dual-opteron is probably reasonable.
that's real dissipation, of course - call it 45W when measured at the wall.

> > I managed to hook up my kill-a-watt to a dual opteron 2.6 GHz, 4GB pc3200,
> > and a 73GB scsi disk (a sun v20z).  The highest power consumption I
> > could find was was running 1 distributed.net client per cpu.
> > 
> > The results was 197-198 watts and 200-201 VA.  I'm quite impressed,
> > our 2.2GHz version of the same box is in the 270-300 watt range.