I have seen on many forums that ACPI makes a lot of troubles to a lot of users under Windows. I will try to explain several things about ACPI and I hope that you will be able to solve your problems after you read this article. I cover only most encountered issues, but always there is a choice even if it's called ACPI disable.:)

What is ACPI?

Users should be aware that ACPI does not improve performance or reliability. If there is a thing that it can improve that thing is called functionality. ACPI is an abstract hardware interface that provides a standard way to integrate power management in a PC system, including hardware, operating system and application software. The advantages of ACPI are obvious, but may not be required for all users. With ACPI functions you can turn peripherals on and off, power-on the system on external activities like the ring of the telephone, etc. Without any doubt it may be a very useful feature, but does it worth?

The reasons why you should use ACPI are multiple, but the most important are:

• ACPI provides a new advanced Plug and Play environment for today computers
• ACPI uses it's own language so it's supported by other operating systems
• ACPI is not Microsoft property :)
• ACPI provides control of Power state
• ACPI use the System Control Interrupt (SCI)
• ACPI should make your life easier because it handles the resources problems
• ACPI should allow you to insert / remove devices in the fly

How do I use ACPI in Windows 2000?

In order to use ACPI in Windows 2000 you must have it enabled in BIOS at the setup stage. Win 2K use a different HAL (Hardware Abstraction Layer) for ACPI enabled machines! Assuming that you installed Windows 2K with ACPI support and you want to disable ACPI in BIOS you will realize that your computer won't boot. Normally most motherboards provide ACPI enable / disable settings in BIOS but there are several which do not allow the user to disable the ACPI support. When something goes mad apparently you can not get rid of ACPI. Just apparently, because there are solutions.

The computer ACPI support is detected in the setup stage, but there are less frequent cases when ACPI is not detected and the Standard PC HAL is installed. If you want to force the installation of the ACPI HAL:

1. At the blue screen of the Windows 2000 setup when it prompts you to press F6 for additional mass storage devices press F5 and you will have a list of options.
2. Choose the proper HAL for your machine remembering that there are also different HALs for multiprocessor machines.
3. Complete the setup, go to Setup / Control Panel / System / Hardware / Device Manager / Computer. If you have listed the Advanced configuration and Power Management (ACPI) the process was completed successfully.

Warning: You can do the same thing if you don't want to install ACPI and your BIOS doesn't support ACPI disable setting. Just choose the Standard Computer HAL from the list of options.

Another method to disable ACPI is:

• wait for the text-phase of Win2K setup to complete
• before W2K Setup Wizard to load, boot into DOS and change ACPIEnable = 0 from ACPIEnable = 1 in file c:\txtsetup.sif

The reason why ACPI is not installed on a computer with known ACPI compatibility may be a Microsoft known subtle incompatibility which can lead to hardware instability. In the installation step Windows 2000 checks the BIOS compatibility with ACPI and the BIOS presence on a known bad list. If the BIOS is there ACPI is not installed. Of course than errors can occur so you can force the ACPI installation (not recommended).