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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