John Galea's Windows 95 Power Management Page
Introduction
Power management can be rather confusing to understand given the different
levels that it occurs on, and the different devices that are supported
for power management. In the end, once you have it all figured out, do
you really care? After all on a desktop it's not like when you on a laptop
when every last watt of power is coming from a limited battery. The amount
of money you save is probably not even measurable. That EPA thought is at
a much grander level. You also need to keep in mind, for each power management
mechanism, there is a break even point. As you can imagine if you turned
off your hard drive or monitor every minute or two, the wear and tear
on them would cost you (and the environment) far more than you save. You
need to find a level of power management you are comfortable with. That said,
lets dive into power management.
Here I am only going to discuss desktop power management. Not laptops. Laptops
generally have a lot of code written for them to all complete power management
that is not supported on desktops. This would include items such as a complete
dump of memory (RAM) to the hard disk so that the memory can be powered off
as well. Some companies such as IBM have included some of these deep power
management features on desktops, but this would be the exception, not the rule.
BIOS
Bios (or CMOS setup as it is sometimes called) is the primary place where your
power management is defined. Additionally, BIOS is where you define when
you want to come out of power management. Typically you would come out
of power management if a keyboard was hit, a mouse was moved or the phone rang.
In the office there may be other events such as network events as well. You
also may be able to specify a time to come out of power management. Your
first step will be to go into your BIOS setup and set your power management
to levels you think are reasonable.
Devices for Power management
So what part of my computer supports power management. Generally speaking
there are three areas which are the most common place for power management:
- your processor
- any Pentium processor, or newer 486 will support various forms of power
management including processor slowing to various degrees and all the way
up to a complete processor suspend. In this mode the processor is
completely stopped. Note that when the processor comes out of suspend it
does so in one hell of a hurry. This can cause quite a spike of power, which
over time could have negative effects, but heh, in Intel we trust right?
- your local bus (including both VESA and PCI) are directly tied to your
processor bus. So slowing your processor, also slows (and thus power manages
the devices on the local bus). PCI actually support a complete stopped clock.
The ISA on the other hand is far too old for such an old concept, so any power
management that would go on with an ISA card is specific to that ISA card. He
what do you want for a bus that is as old as an 8086 or 80286!
- with all this said, processor power management is probably stealth power
management, because with the exception of the elusive suspend, your
system may transition in and out of the slower speeds to fast you
don't even notice it. I haven't even been able to find a program to
display the current state, although I'll bet there is one somewhere.
- manual suspend (discussed a little later) is quite easy to note because
the system takes some time to comes out of suspend, and on my system
actually beep going into and coming out of suspend. I however, have not
managed to get my system to go into suspend on it's own when windows is
running. Works fine outside of windows though.
- older 486's did not support the power management routines and were
supported only by a special version of the 486 used only in laptops called
the 486SL. Later 486's rolled these functions and made the processor core
static. Which is have you'll have to discover yourself.
- hard disks
- most newer hard disks (basically greater than 340MB will probably have it) allow
the hard drive to enter a spin down mode when they have not been used for
some period of time. Not all drives support this, and I have had trouble with
very old drives with power management turned on. It actually caused troubles
at resume time. That said, if all your drives support power management then
you will actually see the individual drives powered up and down as needed.
So if your operating system was on one drive and data on another and you
were busy doing something that didn't involve the data drive, the data drive
might actually sleep while you were busy. This is how it works on my ASUS
P55T2P4 motherboard. You want to be careful not to have the power down
time to be set rather high. If the drive is constantly powering up and
down, it's probably worse for the drive. I have mine set on max time.
- this power management is easy to detect because you generally can
hear the hard drive spin up and down as it enters/leaves power management.
You will also see a pause while you wait for the drive.
- while were on the topic of hard drives I'll take a moment to babble.
Most modern Pentium based machines have an enhanced IDE controller that
supports bus mastering. What this means is that the processor is not needed
to transfer data to and from the hard disk. This is done completely by the
controller. On older systems only PIO was supported and this required the
processor to do all data transfers. So why am I bothering to mention this?
Because the default driver for Windows 95 and OS/2 do not support bus mastering.
You need to load the bus mastering IDE driver for your machine.
- monitor power management
- at last a simple topic and one where you can save a little. If your
video card supports what is called VESA DPMS (Display Power Management System)
and your monitor also supports it, and you have enabled it in BIOS for outside
Windows 95, and enabled it in Windows for when your in Windows 95, you monitor
can enter one of three modes. Full on, Low power mode (defined as less that 30 watts.
For your reference the average light bulb is 60 to 100 watts) and lastly
Shut off. Shut off is basically the same whether the user has turned off the
monitor or the program has with one exception. Monitors often have a heavy
click when turned on by the user. This is a demagnetizing cycle called
degaussing. This is automatic on some monitors, manual on others and some
don't even have it. When the monitor leaves the shut off mode from power management
the degaussing cycle will not be run. I personally believe shut off should
only be used if you are going to be away for a long time (greater than 1 hour).
Low power mode is excellent on most new monitors.
Windows 95 Power management
Ok now all this is defined we can finally talk about Windows 95 power
management. To see if power management is installed on your system
go into My computer, Control Panel. Look for an icon called Power. If
it is not there, we need to check if APM (Advanced Power Management)
is supported and enabled. Go into My computer, Control panel, System, then
Device manager tab, then pick on the + beside System devices. Look for
Advanced Power Management. If it is not there, then your system does not
support it. If it is select the APM, and then select Properties, then
Settings tab. Check if it is enabled.
If power management was not enabled in BIOS when you did your install or if
you upgraded your motherboard from one that did not to one that did, and
probably a number of other reasons, then Windows will not install the
Power icon into your control panel. I checked about and the word from
Microsoft is that to install this there is only one way. Enable the power management
in BIOS, enable it in system properties and ... Reinstall windows. You have
got to be kidding. Nope that's the word, and it seems to be right. I tried
everything I could think of to get around this and eventually gave in and
reinstalled Windows and there it was, the Power Icon.
Windows 95 Processor Power Management Settings
Go into My computer, Control panel, Power. You have two items your can
change here. One is the Power Management mode Off, Standard and Advanced.
You'll have to play to find the one that works best for you. The second item
if you can have Windows show a suspend choice on the shutdown window. This
allow you to put your processor, and local bus cards into suspend mode manually.
This works well and with the BIOS set it will come of of suspend quite well too.
As mentioned earlier though, I have not been successful in getting the system
to enter suspend on it's own in Windows. Works fine outside Windows (BIOS is fully
in control at that point).
The values specified for your processor power management in your BIOS
will be allowed to work with this set properly in Windows.
Windows 95 Hard disk Spin down
This is a straight whatever set in your BIOS and Windows neither
controls, nor interferes with these settings.
Display Power Management
There are two ways to control power management of your display.
The new way and the old way.
In the old way (Windows 3.x method)
the screen saver you chose either supported DPMS or didn't. If it
did then you simply enable and set the power management you want.
The new way is that you tell Windows 95 that your monitor supports
power management by selecting My computer, Control panel, Display,
Settings tab, Change display type button, and click the check box that
says you monitor is energy star compliant. This is EPA term for a monitor
that supports DPMS and is below the 30 watt number. Once this is set
the Energy savings features should be able to be defined in
My computer, Control panel, Display, Screen saver tab.
Summary
In then end, once you have figured it all out, do you really care, well
for me it's just something that was there that I wanted to explore and work
correctly. Enjoy, hope this helped and be sure to email me if you liked
what you read. Of course suggestions are welcome, criticisms can be sent to
someone else, anyone else ...
Warning
If you are having trouble getting your power management working correctly
there are a number of programs that can interfere with power management.
Sound execution on the command to enter manual suspend will cause
suspend to start and immediately come back out of suspend.
Deskmenu from Microsoft seems to interfere with both hard disk power management
and display power management. I'm sure other programs will too, so if power management
is working as expected, try to start removing programs from memory to see if
you can find the offending program.
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