How To Fix ACPI Error (Stop Error 0x000000A5...)

Stop errors (also called blue screen errors or blue screen of death errors) are the most severe errors Windows can encounter. They occur if a serious problem causes your Windows system to shut down or restart unexpectedly. You might see a message that says
"A problem has been detected and Windows has been shut down to prevent damage to your computer"
These errors can be caused by both hardware and software issues, and it can be difficult to troubleshoot the problem. In reality, the most common cause of blue screen errors is a device driver problem. Outdated, incorrect or corrupt drivers can cause the system to encounter a Stop error. You can use a driver update program to check, find, download and update all device drivers automatically.

What is the ACPI BIOS ERROR

The ACPI_BIOS_ERROR bug check has a value of 0x000000A5. This bug check indicates that the Advanced Configuration and Power Interface (ACPI) BIOS of the computer is not fully compliant with the ACPI specification.

The variances between ACPI in the BIOS and in the operating system can cause different outcomes in different systems when simultaneous I/O read/write operations are attempted. These outcomes are usually determined by whether the system’s ACPI BIOS is compatible or not with Windows.

What is ACPI?
The Advanced Configuration and Power Interface (ACPI) is a part of the BIOS and the operating system. The presence of ACPI in the BIOS on a given Windows system determines whether this system can make full use of features such as Power Management and Plug and Play (PnP).

The Power Management applet, accessed in the Control Panel, lets you control power usage and power savings. For example, you can configure a system to go into hibernation (sleep mode) after a preset time period, or to restore power at the touch of a button.
 ACPI has its uses on all systems, but it's particularly beneficial on laptops, where power management can be crucial. ACPI also interacts with PnP and can help PnP routines successfully load drivers for PnP devices.

The ACPI BIOS ERROR involves interaction between the BIOS and the operating system via the Hardware Abstraction Layer (HAL) driver. To fully understand what's going on, let’s take a deeper look at how ACPI in the BIOS (ACPI BIOS) and in the operating system (ACPI OS) talk to each other in situations that might give rise to this error.

Traditionally, ACPI BIOS implementations try to manipulate hardware resources directly through BIOS code. When the ACPI BIOS tries to access and/or modify the hardware resources at the same time as the operating system, an imbalance arises because these operations can't be synchronized. This imbalance can give rise to system instability and/or a hung machine, which needs to be shut down. It's at this point the user is likely to see a STOP: 0x000000A5 or Stop 0xA5 or ACPI_BIOS_ERROR message.

Before Windows XP, this error would often be unrecoverable, and the machine would crash with a blue screen. So, although the error is annoying, at least it's an improvement over the previous situation.

 HOE TO FIX THE ACPI BIOS ERROR

The following suggestions can help you resolve the ACPI BIOS ERROR:

Flash the BIOS:
Flashing the BIOS means you need to find, download, and apply the latest BIOS update for your motherboard. These updates are usually ready for download from the website of your motherboard's manufacturer. If you’re not sure which motherboard and BIOS you’re using, this information is presented on the screen when you first boot a system. Just write it down and go from there.

A potential problem with this solution is that the latest BIOS updates don't always correct these types of ACPI problems. This is because different motherboards run different chipsets, which in turn run different BIOS, and it’s up to the manufacturer to decide when to release a given update. Whether that BIOS update will actually include the required ACPI version update can be anyone’s guess. For more information, you should contact technical support at your motherboard's manufacturer.

Load the default BIOS settings:
If flashing the BIOS doesn’t work, you can also try to load the BIOS’s default settings. Most BIOS interfaces have an option to "Load Safe Defaults". This may remedy the situation, or at least give you general stability so that you can tweak various other settings and restore normal operations.

Disable ACPI:
A further step is to disable ACPI in the BIOS, if the BIOS allows this procedure. If you do, you may lose all ACPI-related functions in the operating system, and you may not be able to boot your Windows system at all. So use this measure with great caution.