On Fri, 13 Jul 2007, Greg Lindahl wrote:
On Fri, Jul 13, 2007 at 08:48:02AM -0400, Robert G. Brown wrote:
Anyway, if a DIMM draws and average power of (say) 10W and is expected
to be on for 3 years, that means it costs roughly $30 over its lifetime.
A few years ago we were trying to estimate power consumption by
DIIMMs, and found that the measured number was much lower. Apparently
they aren't all "on" all the time. So you can't estimate it the way
you're all doing it.
Oh, I believe you. They don't have a heat sink, after all, and if a
DIMM were burning 10W in 8 chips I think it would get pretty hot. I was
just stating a number for the sake of argument. If they really burn
only 3-4 watts, well, that cuts the marginal advantage down to only a
few dollars per DIMM per year.
FBDIMMs seem to be "on" quite a bit more.
I'd love for someone to whip out a kill-a-watt and start comparing the
same machine at different dimm counts.
I honestly think that this is the only way to get a good measure. At
different (memory) loads, too -- I wouldn't be surprised if energy
consumption in RW mode is higher than in refresh-only mode. However,
my KaW is in use on a machine I don't want to turn off right now and I'm
pretty busy doing other things. Anybody rigged to do the experiment?
rgb
-- greg
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Robert G. Brown http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
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