On Feb 16, 8:06*am, Jim Wilkins wrote:
On Feb 15, 11:57*pm, "Michael Koblic" wrote:

...Kill-A-Watt ...
My most recent purchase (Compaq Presario) does this:

Turned off * * * * * 2.1W
Booting * * * * * *60W
On but quiet * *46W
Asleep * * * * * * * * 5.8W
Hibernating * * * *1.7W

My old computer also draws about 3W while supposedly switched off.

So the questions a .......
--
Michael Koblic,
Campbell River, BC

In a discussion on alt.energy.homepower someone (Neon John?) wrote
that they had tested a Kill-A-Watt against lab equipment and found it
quite accurate, but like any digital instrument you can't trust that
the accuracy is as good as the resolution. If the 0.01 Amp display
resolution matches that of the A/D converter (doubtful) then the
wattage at 120V would change in steps of 1.2W and the real accuracy is
no better than +/- one step.

1) Why is the computer drawing any power at all when turned off?

The circuit that commands the computer to power up when you press the
momentary-contact power button has to draw some power itself. I
believe they were designed for lowest cost rather than efficiency. The
service manual for my Dell Dimension says to press the power button -
after- unplugging the AC cord to discharge a large capacitor, before
swapping parts.

2) Why is the power drawn less when hibernating then when switched off?

See above. Your 2.1W and 1.7W readings don't really mean that much
unless you have checked the calibration of that KAW somehow, like with
a resistor load. Which I don't suggest. Even if you do the cheap
methods of converting 120 - 240VAC to a small amount of low voltage DC
can have high power factors.

3) What happens to a computer which is turned off and the plug is pulled?

The front-panel button won't turn it on until you restore AC power.

I have a main power strip on the side of this table that cuts off
everything, slays the energy vampires. (OK, I'm a fan of Joss Whedon's
work). The UPS and laptop charger are plugged into it, and sometimes a
soldering iron and small heat gun. The two desktops are on separate
strips plugged into the UPS. To use one I turn on the main strip, then
the UPS and let it self-test, then the strip for that computer. Their
monitors, USB drives, speakers, printers and keyboard lamp more than
double the power demand.

4) What happens with laptops? Do they draw power from their battery
continuously even when turned off?

This Latitude doesn't, the batteries stay at 100% when it's shut down
or in hibernation. Standby does use some battery power.
I recently had to replace the 2032 CMOS batteries in my 10-year-old
Compaq laptops. Their main batteries are dead so I run them off AC and
they wake up from hibernation with no battery installed, usually the
instant I plug in the charger. Ergo they must not need battery power
in hibernation. The only symptom of the dead CMOS battery was the 1980
date.

jsw

Hibernation is basically off with the previous state of the computer
written to disk, so no power needed to maintain that state. It's got
a flag that tells the boot code that it was in hibernation, so it goes
and loads that state up and theoretically, you're back where you
were. Occasionally, the disk write goes haywire and it can't
successfully read the hibernation file, so you end up like you would
from a cold boot. Standby just powers the CPU and peripherals down to
minimum power required, but maintains the memory contents as-is.
Nothing written to disk. If you pull the plug, you've just lost all
open files and changes. I hate standby. The trade-off is the almost
immediate response when resuming, no need to read a hibernation file
or run POST, it just powers up the CPU and disk and starts where it
left off.

Laptops probably draw current when "off", they're checking that power
button just like their big brothers. You could find out how much by
connecting the wall wart power supply to the watt meter, get a not-
connected figure, remove the battery from the laptop and then connect
the power plug to it and get that figure. It isn't going to be much,
might be less than what the wattmeter can read. If the battery is in,
the charger is going to be trickling power into it to keep it charged.

Stan