POWER.EXE and Advanced Power Management (APM) Support (96560)



The information in this article applies to:
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q96560

SUMMARY

You can install the Power program (POWER.EXE) even if your BIOS does not support the Advanced Power Management (APM) specification. After you install POWER.EXE in the CONFIG.SYS file, the POWER command (without any switches) provides status information.

On systems without APM support, POWER displays the following:
   Power Management Status
   -----------------------
   Setting = ADV:REG
   CPU: idle 90% of the time
On systems with APM support, POWER displays the following additional information reported by the BIOS:
   Power Management Status
   -----------------------
   Setting = ADV:REG
   CPU: idle 90% of the time
   AC Status: OFFLINE
   Battery status: High
   Battery life (%): 90

MORE INFORMATION

POWER.EXE detects whether your system has an APM-compliant BIOS and then adapts accordingly.

When POWER.EXE detects that your system is idle, it saves power by issuing a CPU HALT instruction. HALT stops CPU execution until the next hardware interrupt occurs (this is usually the timer interrupt, which occurs 52 times per second). On systems without an APM-compliant BIOS, testing reveals a 5% power savings.

If your system has an APM-compliant BIOS, POWER.EXE communicates with the BIOS. Depending on the frequency of the idle signals from POWER, the APM-compliant BIOS can save power by shutting down the display or hard disk, switching the processor to a slower speed, or suspending the system entirely.

Modification Type: Major Last Reviewed: 11/19/1999
Keywords: KB96560