__rdtscp

Article
08/03/2021

Microsoft Specific

Generates the rdtscp instruction, writes TSC_AUX[31:0] to memory, and returns the 64-bit Time Stamp Counter (TSC) result.

Syntax

unsigned __int64 __rdtscp(
   unsigned int * AUX
);

Parameters

AUX
[out] Pointer to a location that will contain the contents of the machine-specific register TSC_AUX[31:0].

Return value

A 64-bit unsigned integer tick count.

Requirements

Intrinsic	Architecture
`__rdtscp`	x86, x64

Header file <intrin.h>

Remarks

The __rdtscp intrinsic generates the rdtscp instruction. To determine hardware support for this instruction, call the __cpuid intrinsic with InfoType=0x80000001 and check bit 27 of CPUInfo[3] (EDX). This bit is 1 if the instruction is supported, and 0 otherwise. If you run code that uses the intrinsic on hardware that doesn't support the rdtscp instruction, the results are unpredictable.

This instruction waits until all previous instructions have executed and all previous loads are globally visible. However, it isn't a serializing instruction. For more information, see the Intel and AMD manuals.

The meaning of the value in TSC_AUX[31:0] depends on the operating system.

Example

#include <intrin.h>
#include <stdio.h>
int main()
{
    unsigned __int64 i;
    unsigned int ui;
    i = __rdtscp(&ui);
    printf_s("%I64d ticks\n", i);
    printf_s("TSC_AUX was %x\n", ui);
}

3363423610155519 ticks
TSC_AUX was 0

END Microsoft Specific