Legacy Document

Inside Macintosh: Devices /

Chapter 6 - Power Manager / Power Manager Reference

Power Manager Dispatch Routines / Determining the Power Manager Features Available

PMFeatures

You can use the PMFeatures function to find out which features of the Power Manager are implemented.

unsigned long PMFeatures();

DESCRIPTION

The PMFeatures function returns a 32-bit field describing hardware and software features associated with the Power Manager on a particular machine. If a bit value is 1, that feature is supported or available; if the bit value is 0, that feature is not available. Unused bits are reserved by Apple for future expansion.

Bit name	Bit number	Description
hasWakeupTimer	0	The wakeup timer is supported.
hasSharedModemPort	1	The hardware forces exclusive access to either SCC port A or the internal modem. (If this bit is not set, port A and the internal modem can be used simultaneously by means of the Communications Toolbox.)
hasProcessorCycling	2	Processor cycling is supported; that is, when the computer is idle, the processor power will be cycled to reduce power use.
mustProcessorCycle	3	The processor cycling feature must be left on (turn it off at your own risk).
hasReducedSpeed	4	Processor can be started up at a reduced speed in order to extend battery life.
dynamicSpeedChange	X	Processor speed can be switched dynamically between its full and reduced speed at any time, rather than only at startup time.
hasSCSIDiskMode	6	The SCSI disk mode is supported.
canGetBatteryTime	7	The computer can provide an estimate of the battery time remaining.
canWakeupOnRing	8	The computer supports waking up from the sleep state when an internal modem is installed and the modem detects a ring.
hasDimmingSupport	9	The computer has dimming support built into the ROM.

ASSEMBLY-LANGUAGE INFORMATION

The trap is _PowerMgrDispatch ($A09E). The selector value for PMFeatures is 1 ($01) in the low word of register D0. The 32-bit field of supported features is returned in register D0.