[Beowulf] 90nm opteron power usage

[Mark Hahn]

> 22 watts for ONE dimm is significant. for a motherboard with 8 such
> dimms you end up with a rather huge power budget.

hmm, I thought I was clear: the correct expected max dissipation is 
about 5W per dimm.  the theoretical max for an unusual configuration,
achievable only on a dimm-testing rig would ~22/dimm.


> > > 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.