Legacy Document

Inside Macintosh: Devices /

Chapter 6 - Power Manager / Power Manager Reference

Power Manager Routines / Controlling the Idle State

GetCPUSpeed

You can use the GetCPUSpeed function to read the current CPU clock speed.

FUNCTION GetCPUSpeed: LongInt;

DESCRIPTION

The GetCPUSpeed function returns the current effective clock speed (in megahertz) of the CPU.

ASSEMBLY-LANGUAGE INFORMATION

The MPW development system provides an assembly-language macro to execute the GetCPUSpeed routine. That macro calls the _IdleState trap. To call the _IdleState trap directly, you must first put a longword routine selector in the D0 register. For GetCPUSpeed, the routine selector can be any value that is less than 0. The CPU speed is returned as a single byte in register D0.