The assumption is wrong. A server motherboard and CPU draws the same power
regardless of what it's doing. Lap-tops and the like are different and you
actually pay extra for that design. Most circuts these days are nmos
technology. Only in cmos does the power go up with the frequency. Peripheral
usage, like disk drives, are also constant since the largest power draw goes
to keeping them spinning. The seek mechnics are trivial. Floppy drives and
cd-rom drives are different. But, most servers do not keep those spinning
constantly. Ergo, for all intents and purposes, servers are a constant power
draw. They can be rated.
But, isn't this a topic for the DataCenter list?
Once upon a time, Roeland Meyer <rmeyer@mhsc.com> said:
The assumption is wrong. A server motherboard and CPU draws the same power
regardless of what it's doing. Lap-tops and the like are different and you
Not necessarily. For example, when a server is idle, Linux "halts" the
CPU between interrupts (instead of doing a "busy wait" loop). This
significantly drops power usage and heat generated, which can also mean
lessfan power.
So, a busy Linux server generates more heat and uses more power than an
idle Linux server.
I think FreeBSD does the same; I don't know about other OSs.
The assumption is wrong. A server motherboard and CPU draws the same power
regardless of what it's doing. Lap-tops and the like are different and you
actually pay extra for that design. Most circuts these days are nmos
technology. Only in cmos does the power go up with the frequency. Peripheral
Nope. Most are CMOS and the power goes up for both NMOS and CMOS
with increasing clock frequency.
That may not change your conclusion though.
usage, like disk drives, are also constant since the largest power draw goes
to keeping them spinning. The seek mechnics are trivial. Floppy drives and
cd-rom drives are different. But, most servers do not keep those spinning
constantly. Ergo, for all intents and purposes, servers are a constant power
draw. They can be rated.
Chris
Yes, but is it *really* measurable?
I mean, are we talking a difference of more than a watt (in a machine that
already pulls 80 to 120 watts)?
1% difference in power consumption could be related to someone passing
wind in the building on the same power grid.
From: Roeland Meyer <rmeyer@mhsc.com>
Subject: RE: Forcasts, why won't anyone believe them?
Date: Tue, 16 Jan 2001 19:49:45 -0800
The assumption is wrong. A server motherboard and CPU draws the same power
regardless of what it's doing. ...
I am just a software guy, but I believe that most _systems_ have a large
current draw when they are powered up, (e.g., all those fans, some of
which are pretty large).
I believe that the original comment was observing that there is often
quite a difference between the rated (peak) load offered by a device and
the average load. Both are useful to know.
(I assume that everybody, sometime in their career, has learned about the
difference between peak and average load when they tried to power up all
of their routers at once and popped the breakers.)
-tjs
:Nope. Most are CMOS and the power goes up for both NMOS and CMOS
:with increasing clock frequency.
Let's not split any more hairs. xMOS power consumtion is tiny and
irrelevant to the original context of this thread.
-brian
Mac OS [9|X] has very fine grain control over the CPU speed. This is
utilized on laptops for enhanced battery life, and on desktops for lower
power use and heat generation.
For a real example, the digital thermometer sitting on top of my G4 cube
shows about 84 F while it idles. When I launch dnetc to start cracking RC5
keys, the air temp above the grill (no fan on this machine) rises to 97 F
within about 5 minutes.
Since I'm plugging the Mac, I might as well also point out that the latest
773MHz G4s use 17 Watts max load. I'm often dissapointed that Apple doesn't
do more to tout the energy efficiency of their hardware.
-pmb
Hmm.. 17 watts. Of course, that's just the CPU, but I just noticed that
where I'm working right now is primarily lit by 2 22-watt flourescent lights..
So.. How many of you kill the flourescents in your back-office cubicle
farms during a California-style power crunch? 
For that matter - send the cubicle critters home. You ever *looked* at
how many watts the average human body outputs?
Valdis Kletnieks
Operating Systems Analyst
Virginia Tech
> Since I'm plugging the Mac, I might as well also point out that the latest
> 773MHz G4s use 17 Watts max load. I'm often dissapointed that Apple doesn't
> do more to tout the energy efficiency of their hardware.
Hmm.. 17 watts. Of course, that's just the CPU, but I just noticed that
The CPU chips on the previous G4s use only about 4 or 5 watts (I suspect
it hasn't changed much).
It's a lot less than a P3 because it's RISC vs CISC chips.
where I'm working right now is primarily lit by 2 22-watt flourescent lights..
So.. How many of you kill the flourescents in your back-office cubicle
farms during a California-style power crunch? 
For that matter - send the cubicle critters home. You ever *looked* at
how many watts the average human body outputs?
Valdis Kletnieks
Operating Systems Analyst
Virginia Tech
Most people I know don't power their bodies from a wall socket...
Of course, people that spec A/C do indeed take into account the heat
generated by the occupants.
Regards
Marshall Eubanks
Multicast Technologies, Inc.
10301 Democracy Lane, Suite 201
Fairfax, Virginia 22030
Phone : 703-293-9624 Fax : 703-293-9609
e-mail : tme@on-the-i.com http://www.on-the-i.com