[Beowulf] /. Cooler room or cooler servers?

Mark Hahn hahn at physics.mcmaster.ca
Thu Apr 7 19:27:30 EDT 2005

> > > No mention of PowerPC which runs far cooler (1/2?) than Intel/AMD:
> >
> >except that it doesn't.
> >
> > > http://www.terrasoftsolutions.com/products/apple/power-useage.pdf
> >
> >lovely graph.  alas, the numbers are pure fantasy.  yes, I actually
> >did measure a dual xserve g5 (not heavily configured) and it was 200-210W,
> >quite comparable to dual-opterons and even dual-xeons.
> Leaving aside such tantalizing issues as what is a GHz, in terms of useful 
> work.

is there some reason to believe I'd deliberately arrange an unfair
comparison?  in any case, these factors don't matter that much.
the point is that the true dissipation of 200-210W is drastically differt
from the macophile reputation of these machines.  at the time, what 
I had to compare with were duals like HP Dl145 (8G, 1.8's).  iirc
those are around 220W; the same machine with a 2.2 peaks at 240.
obviously, the new opteron rev would be noticably cooler.

> However, if we do a straight watts/GHz, Xeon is 34.375, G4 is 33.8 ... not 
> too much difference.

I'm not sure where those numbers come from - I hope you're not just using 
Intel's TDP numbers (which are not max-dissipation numbers.)

W/GHz is amusing; here are some other numbers:

		w	ghz	w/ghz
amd		143	2.2	65
intel sc	214	3.0	71.3
intel dc	242	2*2.8	43.2

of course, the AMD looks even better if you scale by performance rather than clock.

> One also needs to look at important ancillary issues like power consumption 
> of the cache, bus drivers, etc.  And, of course, instruction stream makes a 
> big difference.

kind of obvious, don't you think?  when I said peak, I meant peak,
and I'm quoting power dissipation measured at the wall plug (kill-a-watt).
for these systems, running two compute-intensive programs maxes out;
messing with memory or disks only adds a few watts (percent).

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