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Enabling ACPI Support Under Windows 98
David Yee and Hiep Ma, 10 September 1999

ACPI stands for Advanced Configuration and Power Interface, and its support is one of the new features of Microsoft Windows 98. ACPI is meant as an improvement over the Advanced Power Management (APM) that is found in Windows 95. ACPI allows for the operating system to have control over all aspects of power-management. For example, Windows 98 can have control over the function of the power button. You can have the computer go into standby mode, hibernation mode, or simply turned off when the power button is pressed.

The "hibernation" mode is especially exciting. It is part of a feature which Microsoft calls OnNow. Basically when the computer goes into hibernation, everything in memory is written onto an image file to the hard drive, and the machine is turned off. But when you turn the computer back on, the image file is loaded and Windows 98 along with your desktop are right there- the actual boot up process is eliminated. Hiep has seen this work on a Toshiba notebook- when the laptop comes out of hibernation, Windows 98 "loads" in something like 15 seconds. So if you're typing a paper or playing a game and you put the computer into hibernation, when you turn the machine on later you're right back typing the paper or playing that game exactly where you left off. Really cool indeed.

***UPDATE September 10, 1999: In order for hibernation to work, your hard drive needs to be partitioned FAT16. According to Microsoft, FAT32 does NOT support hibernation. But I have received an email from a reader that he has gotten hibernation to work with FAT32, so who knows :-). Microsoft is planning to support hibernation with FAT32 in Windows 2000, however.

In order to use the nifty ACPI features in Windows 98, you first must have an ACPI-compatible BIOS. If you have it, upon boot up the BIOS description usually will say "ACPI BIOS". Once you know you have it, then proceed to disable APM in the BIOS to prevent possible conflicts. Next, you have to enable ACPI in Windows 98. For some reason or another, Win98 does not appear to support ACPI by default- you must force the OS to detect your ACPI BIOS. This can be done one of two ways:

1) When you are upgrading to Windows 98, run setup in a DOS prompt with the /pj option (i.e. type setup /pj).

2) Run regedit and find the following string in the registry: HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/Current Version/Detect. Create a new string value called ACPIOption and set it equal to 1.

2)con't Then go to the Control Panel and run Add New Hardware. Let Windows 98 do an automatic detection. After the process is finished, click on details and you should see the following:

After rebooting, the Device Manager should show the ACPI BIOS installed:

Now go to the Power Management under Control Panel, and you should see how well you computer supports ACPI. Unfortunately the BIOS for our Asus P2B currently does not support the hibernate feature, and so the hibernation tab, which is supposed to appear between Power Schemes and Advanced, was not there.

Despite this, Windows 98 was able to fully control the action of the power button:

Although our test system did not support hibernation, your computer might- especially if it is very new. We would love to hear about your experience with the hibernation feature of OnNow if you get it to work!

***UPDATE September 9, 1999: Observations, Side Effects and Quirks That You Should Be Aware of After Enabling ACPI: The following are compiled from the responses I've received since the article's publication:

ACPI requires an IRQ, and seems to have an amazing affinity for IRQ 5; people who have Sound Blaster Live! cards probably need to disable the Creative SB16 Emulation after enabling ACPI; people with a Sound Blaster AWE32 may have to disable a COM port; people with a Sound Blaster PCI64 may have to disable Legacy Device for DOS After enabling ACPI and rebooting for the first time, Windows will redetect all Plug-and-Play devices, which can be a bit annoying as you may have to supply diskettes; make sure you have Win98 CAB files on your HARD DRIVE in case they are needed since the CD-ROM drive will likely be unavailable during the re-detection Standby is very quirky- your system will probably successfully enter Standby the first time and you can wake up the system from it, but the second time it likely will fail to enter Standby or will but does not wake up If after installing ACPI you decide that you dislike it and remove it from Device Manager, APM will be re-installed for you by Windows, but I have received emails complaining that systems with APM that used to be able to turn off automatically after Windows shuts down are not able to any more... probably a registry entry preventing that.... Also a few readers have reported the above shutdown problem but using ACPI Some people have reported that Method 2 to enable ACPI does not work, but Method 1 (setup /pj) enables ACPI perfectly

Test System Pentium II-300 and Asus P2B motherboard (BIOS version 1005 Beta 011), 64 Mbytes of PC100 SDRAM, Quantum Viking 4.5 Gbyte ultra SCSI drive with a Diamond Fireport 40, ATI Xpert 98 (8 Mbyte AGP) Drivers used: ATI Xpert 98 (Version 5.20, 06/30/98)

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