"logized" wrote:

"Aniseed" wrote in message
roups.com...
Sure, its possible to look up what one's CPU consumes, but there are
several hardware and software components drawing power, and it quickly
becomes difficult to know how much is really being consumed.

I'm particularly interested in the consumption of a lighlty equipped
PentiumPro machine which is on all the time, no monitor. It is
passively cooled, and the heatsink feels quite cool to the touch, so i
am hoping it is below the 50W mark.

I also have a P4 1.8GHz machine with 2 HDDs and a 21" CRT, I'm curious
to find out how much it really consumes, and how it compares to the
value from manufacturer's specs.

Herminio


I have measured the consumption of an old machine fitted with a 400Mhz amd
cpu at between 40-60W and a Cyrix "300" machine at 38W - these machines have
large heatsinks with a very slow fan (at 5v) and don't produce much heat.
Your cpu may take more power - maybe as much as a Duron 800-900Mhz - so may
be worth checking further - see
http://www.geek.com/procspec/intel/pentiump.htm

For the best power efficiency - consider getting a Via EPIA board (various
built-in cpu options 500-1000Mhz).

I suspect the 21" CRT uses a lot of power too.


Hi again,
Yesterday I recieved one of the Maplin Power meters in the post. It is made in
Taiwan, by Prodigit Elecronics Co Ltd. Its of reasonlably good quality build,
given the price.

I've tried it out on stuff around the house. After much bending over plugging
and unplugging things, I've acquired a list of results and a backache. If
anybody is curious, here is what I found out:

monospace font please
Appliance: Reading:
Kettle rated at 1800-2200W 1980W
Desklamp with 60W bulb 58W
PIII Dell Laptop 20W idle
PentiumPro 200MHz, 1HDD 40W idle
Athlon 1.4GHz, 1HDD 90W idle, 105W runing sims2
Pentium IV 1.8GHz, 2HDDs 75W idle, 100W running hl2
22" Iiyama CRT 5W standby, 70-100W on
Lower back Light throbbing
/monospace font please

I can see that the device has correctly measured the kettle and desklamp,
because the reading I get matches their power rating. However I don't know how
accurately it is measuring the various computers and the CRT monitor. I hope it
is accurate, because I was pleasantly surprised to see that the monitor
consumes about 75W when displaying my windows desktop, I thought it would be
higher.

However:
Ian Stirling wrote:
The meters (the cheap ones, the maplin and Lidl 6.99 ones) work out the
current by measuring the voltage/current several times per cycle.
Unfortunately, the lowest cost is got by reducing 'several' as much as
possible.

For things like heaters, or motors, you can almost trivially get a pretty
good reading of power and power-factor (amount current is leading or
lagging voltage) with just 3 or 4 samples per cycle.

This is because the current they draw is a nice sine wave.
Many PC (and other switched-mode PSUs) unfortunately have significant
very fast variations in current.
So, the meter misses these changes, and assumes that the power supply is
drawing a higher current than it should.

So it seems I can't trust the measurements from my device (yet).
Would anyone know where I can learn more about switched-mode PSUs?

Aniseed