Since Jim Wilkins mentioned Kill-A-Watt meter here some time ago it came on
sale at Lee Valley and I got me one. I spent an interesting hour running
around the house finding out what consumes electricity while plugged in and
what does not. What surprised me were the computers.

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
1) Why is the computer drawing any power at all when turned off?
2) Why is the power drawn less when hibernating then when switched off?
3) What happens to a computer which is turned off and the plug is pulled?
4) What happens with laptops? Do they draw power from their battery
continuously even when turned off?

and...

Why has this stupid Windows Live Mail program suddenly decided to type É
instead of a question mark ÉÉÉ

--
Michael Koblic,
Campbell River, BC

Michael Koblic wrote:
Since Jim Wilkins mentioned Kill-A-Watt meter here some time ago it came
on sale at Lee Valley and I got me one. I spent an interesting hour
running around the house finding out what consumes electricity while
plugged in and what does not. What surprised me were the computers.

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

It's endlessly polling itself, to see if you turned it on.

2) Why is the power drawn less when hibernating then when switched off?
3) What happens to a computer which is turned off and the plug is pulled?

Only the CR2032 cell keeping the BIOS settings, stored in CMOS, alive.

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

and...

Why has this stupid Windows Live Mail program suddenly decided to type É
instead of a question mark ÉÉÉ

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

Michael Koblic wrote:
Since Jim Wilkins mentioned Kill-A-Watt meter here some time ago it came on
sale at Lee Valley and I got me one. I spent an interesting hour running
around the house finding out what consumes electricity while plugged in and
what does not. What surprised me were the computers.

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

computers have soft switches. they are never off, just like a TV that has
a remote control. they use a few watts just sitting there. The power
supplies are on, in a low power mode.

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

A 400mW difference is pretty much nothing. A hibernating computer is as
off as they can get while being unplugged. The tolerances of your chinese
power supply before and after warming up could easily cause that
difference.

A computer is a sleep state is more "on" than computer that is off, but
far less active than one that is running and doing stuff.

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

nothing. it uses no power and does nothing.

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

yes. they draw power, but it's very very small- far less than the 1.7 to
2.1 watts a desktop might use when soft-off. The amount drawn is so small
it doesn't even matter in real life.

and...

Why has this stupid Windows Live Mail program suddenly decided to type ?
instead of a question mark ???

no idea.

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

On Mon, 15 Feb 2010 20:57:04 -0800, "Michael Koblic"
wrote:
*Snip*

Why has this stupid Windows Live Mail program suddenly decided to type É
instead of a question mark ÉÉÉ

Votre clavier lui-même remis à "français", la mienne est-ce que
parfois (Win 7).

H.

On Tue, 16 Feb 2010 07:06:35 -0800 (PST), 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.

Switching Mode power supplies are going to throw a monkey wrench in
those accuracy tests. You have to test for that specifically.

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.

You are also supplying power to the Real Time Clock chip so you
don't run down the lithium battery on the motherboard, and the LAN
card and it's "Wake On LAN" circuit used on certain industrial use
machines - print spoolers and the like.

Some computers are also set up to power-up or wake-up when the phone
on the modem rings, or power the modem and answer the line while the
computer is still booting/waking. So it can sleep or hibernate and
still be used as a fax machine, or be remotely polled at 2 AM in a
business setting.

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.

It's a switching-mode power supply, and you might be getting
anomalous low or high readings at those low power levels. Do a little
research on "Q Factor" where power panels with large numbers of
computers burn up the neutral wires and the busbars in the panels.

The power supplies take little nibbles out of each cycle and the
cumulative current on the neutral is higher than the power phase draw
- they don't balance out like normal phase-neutral loads, because each
computer is taking it's nibble at a different moment in the cycle.

More prevalent on 120/208V 3-phase panels. They make special panels
and special "High Q Factor" 480V to 120/208V transformers with
double-sized neutral bussing to handle this. And you double-up the
neutral conductors or bus-bars between them.

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.

All well and good, but you'll be changing the CMOS battery more
often. Better than the old days, when the battery was molded into the
RTC chip, and you have to replace the whole thing.

Okay to kill the power totally to all the other peripherals, but
leave the computer itself plugged in. Plus, you want it to be turned
on overnight at least once a week - especially on Patch Tuesdays, when
Mickeysoft tries to plug all the holes.

I just let it run, they seem to live a whole lot longer that way. So
it costs a few pennies a day, big whoop.

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.

They use a tiny bit too, but they have better power management.

-- Bruce --

"Howard Eisenhauer" wrote in message
...
On Mon, 15 Feb 2010 20:57:04 -0800, "Michael Koblic"
wrote:
*Snip*

Why has this stupid Windows Live Mail program suddenly decided to type É
instead of a question mark ÉÉÉ

Votre clavier lui-même remis à "français", la mienne est-ce que
parfois (Win 7).


Mon clavier did it only in Windows Live Mail - in the word processor it was
"anglais". And stopped doing it once I closed down and restarted the WLM.
Personally, I think WLM is un morceau de merde for many other reasons. Not
as good as the old Outlook Express.

But c'est la vie!


--
Michael Koblic,
Campbell River, BC
- Diploma in Franglais - failed

"Bruce L. Bergman" wrote in message
...

snip

Okay to kill the power totally to all the other peripherals, but
leave the computer itself plugged in. Plus, you want it to be turned
on overnight at least once a week - especially on Patch Tuesdays, when
Mickeysoft tries to plug all the holes.

I just let it run, they seem to live a whole lot longer that way. So
it costs a few pennies a day, big whoop.

It took me a couple of weeks before I managed to stop the bloody thing
waking me up when it felt like it, so no, thanks. It can jolly well patch
when I tell it to. It's not just MS that wants to run when it pleases -
others seem to want to do so, too.

The worst was the Window Media Cent It was waking up every morning doing
its thing and because the software was loaded wrong in the factory, there
was no way to access it. After spending two hours on the phone with HP
support I had to re-load the whole thing including all the programs I put on
myself. I was not best pleased.

I guess you buy cheap crap you gotta expect these things. I would not have
bought it if were not for the good reviews.

--
Michael Koblic,
Campbell River, BC

On 2010-02-16, Michael Koblic wrote:
Since Jim Wilkins mentioned Kill-A-Watt meter here some time ago it came on
sale at Lee Valley and I got me one. I spent an interesting hour running
around the house finding out what consumes electricity while plugged in and
what does not. What surprised me were the computers.

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

Because it is never truly off. There needs to be enough power
on a couple of pins of the power supply so it can sense the pressing of
the button to tell it to turn on. In the old days, the power switch was
on the side or back of the computer, and truly disconnected it from the
power line, so it was truly off. These days, the systems are set up to
close down gracefully and then drop the power from the drives and the
majority of the system board, so it needs a way to have the system board
tell the power supply when it is truly ready to shut off.

Also -- it probably keeps power to the clock chip to keep it up
to date, and keep the coin cell from discharging -- and to keep from
losing the contents of the setup NVRAM, which is usually a CMOS RAM
backed by the coin cell.

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

That one is a good trick. I don't know -- inefficiences
somewhere, perhaps?

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

Once the plug is pulled, it can't sense you pressing the power
button, so it can't turn on. If you shut the computer down, unplug the
power cable, push the button once (which would normally turn it on) and
then re-plug the power cable, it probably will not turn on -- unless
there is something remembering that power switch press kept alive by the
clock chip and NVRAM cell.

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

There is typically a coin cell buried in the computer to retain
the clock chip and the NVRAM settings. If that goes dead, then it
depends on the main battery. If that goes dead as well, the system will
next wake up with no proper sense of time, and the NVRAM settings lost
as well.

Also, the battery is used to power the switch which turns on the
system, though most of the logic in the computer is CMOS instead of TTL,
so it does not draw significant power when it is not changing state.

But the batteries used in laptops are known for self-discharge
anyway -- the batteries draw enough power from themselves to dwarf what
the NVRAM and switch sensor draw.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

How is it turned on - a button ? or a switch. Likely a button which then
means a circuit is alive polling the button and other stuff.
Martin

Michael Koblic wrote:
Since Jim Wilkins mentioned Kill-A-Watt meter here some time ago it came
on sale at Lee Valley and I got me one. I spent an interesting hour
running around the house finding out what consumes electricity while
plugged in and what does not. What surprised me were the computers.

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
1) Why is the computer drawing any power at all when turned off?
2) Why is the power drawn less when hibernating then when switched off?
3) What happens to a computer which is turned off and the plug is pulled?
4) What happens with laptops? Do they draw power from their battery
continuously even when turned off?

and...

Why has this stupid Windows Live Mail program suddenly decided to type É
instead of a question mark ÉÉÉ

On Tue, 16 Feb 2010 18:14:13 -0800, the infamous "Michael Koblic"
scrawled the following:


"Howard Eisenhauer" wrote in message
.. .
On Mon, 15 Feb 2010 20:57:04 -0800, "Michael Koblic"
wrote:
*Snip*

Why has this stupid Windows Live Mail program suddenly decided to type É
instead of a question mark ÉÉÉ

Votre clavier lui-même remis à "français", la mienne est-ce que
parfois (Win 7).


Mon clavier did it only in Windows Live Mail - in the word processor it was
"anglais". And stopped doing it once I closed down and restarted the WLM.
Personally, I think WLM is un morceau de merde for many other reasons. Not
as good as the old Outlook Express.

But c'est la vie!

Upgrade from (spyware?) WLM to M$ Outlook.

--
Note to The O -

You can't build a reputation on what you are going to do.
-- Henry Ford

On Tue, 16 Feb 2010 17:37:23 -0800, Bruce L. Bergman
wrote:

On Tue, 16 Feb 2010 07:06:35 -0800 (PST), Jim Wilkins
wrote:

On Feb 15, 11:57Â*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.

Switching Mode power supplies are going to throw a monkey wrench in
those accuracy tests. You have to test for that specifically.

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.

You are also supplying power to the Real Time Clock chip so you
don't run down the lithium battery on the motherboard, and the LAN
card and it's "Wake On LAN" circuit used on certain industrial use
machines - print spoolers and the like.

Some computers are also set up to power-up or wake-up when the phone
on the modem rings, or power the modem and answer the line while the
computer is still booting/waking. So it can sleep or hibernate and
still be used as a fax machine, or be remotely polled at 2 AM in a
business setting.

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.

It's a switching-mode power supply, and you might be getting
anomalous low or high readings at those low power levels. Do a little
research on "Q Factor" where power panels with large numbers of
computers burn up the neutral wires and the busbars in the panels.

The power supplies take little nibbles out of each cycle and the
cumulative current on the neutral is higher than the power phase draw
- they don't balance out like normal phase-neutral loads, because each
computer is taking it's nibble at a different moment in the cycle.

More prevalent on 120/208V 3-phase panels. They make special panels
and special "High Q Factor" 480V to 120/208V transformers with
double-sized neutral bussing to handle this. And you double-up the
neutral conductors or bus-bars between them.

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.

All well and good, but you'll be changing the CMOS battery more
often. Better than the old days, when the battery was molded into the
RTC chip, and you have to replace the whole thing.


That's not the "good old days" - that's the "in-between nasties". In
the good old days there was a big square CMos battery which could be
replaced with a 4-pack of AA dry-cells.
The self-powered RTC chip was, thankfully, a rather short term
aberation - or was that an abortion.

Okay to kill the power totally to all the other peripherals, but
leave the computer itself plugged in. Plus, you want it to be turned
on overnight at least once a week - especially on Patch Tuesdays, when
Mickeysoft tries to plug all the holes.

I just let it run, they seem to live a whole lot longer that way. So
it costs a few pennies a day, big whoop.

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.

They use a tiny bit too, but they have better power management.

-- Bruce --

On 17 Feb 2010 03:55:58 GMT, "DoN. Nichols"
wrote:

On 2010-02-16, Michael Koblic wrote:
Since Jim Wilkins mentioned Kill-A-Watt meter here some time ago it came on
sale at Lee Valley and I got me one. I spent an interesting hour running
around the house finding out what consumes electricity while plugged in and
what does not. What surprised me were the computers.

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

Because it is never truly off. There needs to be enough power
on a couple of pins of the power supply so it can sense the pressing of
the button to tell it to turn on. In the old days, the power switch was
on the side or back of the computer, and truly disconnected it from the
power line, so it was truly off. These days, the systems are set up to
close down gracefully and then drop the power from the drives and the
majority of the system board, so it needs a way to have the system board
tell the power supply when it is truly ready to shut off.

Also -- it probably keeps power to the clock chip to keep it up
to date, and keep the coin cell from discharging -- and to keep from
losing the contents of the setup NVRAM, which is usually a CMOS RAM
backed by the coin cell.

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

That one is a good trick. I don't know -- inefficiences
somewhere, perhaps?

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

Once the plug is pulled, it can't sense you pressing the power
button, so it can't turn on. If you shut the computer down, unplug the
power cable, push the button once (which would normally turn it on) and
then re-plug the power cable, it probably will not turn on -- unless
there is something remembering that power switch press kept alive by the
clock chip and NVRAM cell.

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

There is typically a coin cell buried in the computer to retain
the clock chip and the NVRAM settings. If that goes dead, then it
depends on the main battery. If that goes dead as well, the system will
next wake up with no proper sense of time, and the NVRAM settings lost
as well.


MOST laptops won't boot properly when the CMOS battery goes dead even
IF the main battery is OK.


Also, the battery is used to power the switch which turns on the
system, though most of the logic in the computer is CMOS instead of TTL,
so it does not draw significant power when it is not changing state.

But the batteries used in laptops are known for self-discharge
anyway -- the batteries draw enough power from themselves to dwarf what
the NVRAM and switch sensor draw.

Enjoy,
DoN.

On 2010-02-18, wrote:
On Tue, 16 Feb 2010 17:37:23 -0800, Bruce L. Bergman
wrote:

[ ... ]

All well and good, but you'll be changing the CMOS battery more
often. Better than the old days, when the battery was molded into the
RTC chip, and you have to replace the whole thing.


That's not the "good old days" - that's the "in-between nasties". In
the good old days there was a big square CMos battery which could be
replaced with a 4-pack of AA dry-cells.
The self-powered RTC chip was, thankfully, a rather short term
aberation - or was that an abortion.

Actually -- that chip was something which Sun kept for *way* too
long. The clock chip actually is a TOD (Time Of Day) clock/calendar,
not a Real-Time Clock which generates precisely spaced pulses for task
switching in time sensitive applications like the CPU controlling a CNC
machine tool. The two terms have gotten mixed up over the years.

The one Sun used (from Toshiba, IIRC) had 2K of CMOS RAM in
addition to the clock and the potted-in cell on machines at least from
the early SPARC-1 machines up through the Ultra-60 in my experience.
The problem was that the RAM contained (in areas inaccessible for write
by the firmwre) the HOSTID and the MAC address (raw ethernet address).
And if you were using licensed software (some compilers and fancy backup
systems were examples which I know of -- probably some database programs
and CAD packages as well) depended on the HOSTID and the MAC address.
It was possible to re-write those sections using a fcode program (FORTH)
keyed into the NVRAM part, but it was a real pain. Each had a bar code
label and you could order a replacement from Sun by barcode number. The
rest of the 2K was used for the eeprom setup variables, and there was a
keyboard sequence during boot to reset the variables to the factory
defaults.

About the time of the SS-2, a company named Solbourne brought
out a semi-clone which had the HOSTID and MAC address in a bipolar PROM,
and the EEPROM and clock were backed by a coin cell which could be
easily replaced. The bipolar PROM was mounted in a socket (as was the
NVRAM/CLOCK chip on the SPARC systems), and if you had to replace a
system board, it came without the bipolar prom -- you were supposed to
swap it over to the new board so your licensed software would continue
to operate.

Yes -- I had to replace a system board in a SS-5 which was
running a licensed compiler, and so I swapped over the NVRAM/CLOCK chip
when I changed. (It helps to have a collection of spare older systems
sitting around when one dies. :-)

The Sun use of the clock/RAM chip started perhaps around 1980 or
so, and continued until the Sun Blade 1000/Sun Blade 2000/Sun Fire 280R
and later UltraSPARC systems, which put most of the information in a
SEEEPROM (Serial Electrically Erasable EPROM) and the clock is powered
by a coin cell in a holder on the system board (plus, of course, the
power supply itself when the system is plugged in. :-)

So -- that Toshiba chip was in service far too long in Sun
systems.


Enjoy,
DoN.

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