Legacy Document

Inside Macintosh: Devices /

Chapter 6 - Power Manager / Power Manager Reference

Power Manager Dispatch Routines / Controlling the Processor

SetProcessorSpeed

You can use the SetProcessorSpeed function to set the clock speed the microprocessor will use the next time it is restarted.

Boolean SetProcessorSpeed(Boolean fullSpeed);

fullSpeed

A Boolean that sets the processor speed to full speed (true) or reduced speed (false).

DESCRIPTION

The SetProcessorSpeed function sets the processor speed that the computer will use the next time it is restarted. If the value of fullSpeed is set to true, the processor will start up at its full speed (the speed returned by MaximumProcessorSpeed, described on page 6-60). If the value of fullSpeed is set to false, the processor will start up at its reduced speed.

SPECIAL CONSIDERATIONS

For PowerBook models that support changing the processor speed dynamically, the current processor speed is also changed. If the speed is actually changed, SetProcessorSpeed returns true; if the speed is not changed, it returns false.

ASSEMBLY-LANGUAGE INFORMATION

The trap is _PowerMgrDispatch ($A09E). The selector value for SetProcessorSpeed is 19 ($13) in the low word of register D0. The Boolean value to set is passed in the high word of register D0. The Boolean result is returned in register D0.

SEE ALSO

You can use the PMFeatures function (page 6-41) to determine whether the computer supports changing the processor speed dynamically.