_umwait
Classification
Other, Miscellaneous, CPUID Test: WAITPKG
Header File
Instruction
UMWAIT r32
Synopsis
_umwait(unsigned int ctrl, unsigned __int64 counter);
Description
Directs the processor to enter an implementation-dependent optimized state while monitoring a range of addresses. The instruction wakes up when the TSC reaches or exceeds the value specified in "counter" (if the monitoring hardware did not trigger beforehand). Bit 0 of "ctrl" selects between a lower power (cleared) or faster wakeup (set) optimized state. Returns the carry flag (CF). If the processor that executed a UMWAIT instruction wakes due to the expiration of the operating system timelimit, the instructions sets RFLAGS.CF; otherwise, that flag is cleared.