Unexpected Results Resuming from Critical Suspend Mode

• Microsoft Windows 98

SYMPTOMS

If your computer goes into Critical Suspend mode, you may experience unexpected results after you resume.

CAUSE

Windows 98 cannot support Critical Suspend/Critical Resume.

This behavior occurs because Windows 98 does not support Critical Suspend/Critical Resume. Windows 98 is capable of sending power management notifications directly to individual device drivers. When your computer is put into Critical Suspend mode, the device drivers are not notified, and as a result, they may not be properly resumed.

This behavior is described in the following section of the Advanced Power Management (APM) Specification:

4.3.9 Critical System Suspend Notification (0008H)

This notifies the APM Driver that the APM BIOS has detected a situation in which the system must be suspended without notification to APM-aware applications. This notification is intended to be used by the APM Driver to perform emergency shutdown actions. The APM Driver must recognize the power management event and then issue the Set Power State function call to set the system state to Suspend without delay, and without notifying its applications or device drivers first.

RESOLUTION

To work around this behavior, use either of the following methods:

• Avoid using Critical Suspend mode in Windows 98. Due to the tighter integration of device drivers and the ability to send power management notifications, Windows 98 Advanced Power Management (APM) is more robust than Microsoft Windows 95 APM. The notification of device drivers is mandatory in ensuring a successful resume.



• Windows 98 includes a Critical Battery Alarm that is set to three percent by default. When your computer reaches three percent, Windows 98 can suspend the computer normally, and you can switch batteries or plug your computer into a wall outlet using the AC adapter, and then resume from Suspend mode correctly.
  
  If you need to implement a BIOS Critical suspend, set the BIOS trip point to two percent or less. This allows Windows 98 to suspend the computer correctly at the three percent Critical Battery Alarm.

MORE INFORMATION

Critical Suspend mode is implemented in the computer's basic input/output system (BIOS). This APM feature enables the operating system to clear the disk cache, and also enables the BIOS to put the computer into a low-power state without notifying any drivers. This results in a very short suspend process. Critical Suspend mode is not designed to be used on a regular basis, but as a way to prevent possible disk problems before the battery completely loses power.

You should normally use Windows 98 Standby mode as it is the only way to ensure that your computer is resumed properly.

A computer will normally first attempt to enter normal Suspend mode after low-battery conditions are detected. This attempt may not work for a number of common conditions, such as when the computer has an active dial- up connection, a disk tool (such as ScanDisk) is active, or the low- battery warning dialog box is currently displayed. This last situation is most likely to occur when the computer has been left unattended. The computer enters Critical Suspend mode, which can result in the above conditions.

For additional information about the APM specification, please see the following Microsoft Web site:

http://www.microsoft.com/hwdev/busbios/amp_12.htm

Keywords          : kbenv win98 winapm 
Version           : WINDOWS:98
Platform          : WINDOWS 
Issue type        : kbprb 

Last Reviewed: February 11, 1999