Getting wrong CPU Processor ID with __cpuid() in Win 11 systems

Question

 

Hello Friends,

 

I am facing an issue in getting CPU Processor ID with C++ code.

I used __cpuid() function as below:

 

---

#include <iostream>

#include <intrin.h>

 

int main()

{

                unsigned __int32  regs[4];

               

                __cpuid((int *)regs, 1);

               

                std::cout << "Processor ID: " << std::hex << regs[3] << " 000 " << regs[0];

}

---

 

This code is working in all the Win 10 systems.

But some Win 11 systems are providing EDX data (regs[3] in above code) as BFCBFBFF.

When I use "wmic cpu get processorid" at command prompt, I got BFEBFBFF.

 

Is it issue with Win 11 system or __cpuid function or any mistake in my code?

 

Please guide me.

Thanks in advance.

 

Regards

Udaya

Answer 1

Hello,

The "__cpuid ()" function works on x86 and x64 architectures. Please check the Windows 11 system architecture.

The information obtained by this function (especially the processor ID) is actually a set of functional identifiers and does not represent a unique serial number or ID of the processor. When "__cpuid" is called with 1, the values in EDX and EAX provide function flags and other processor information. If you need a serial number or a unique processor ID, look it up at the operating system level (for example, using WMIC).

For more information see: __cpuid, __cpuidex | Microsoft Learn

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Answer 2

Hello Udaya,

The __cpuid() intrinsic reads the value from the CPU, whereas the "wmic cpu get processorid" command obtains the information from the SMBIOS.

I don't know why there is a difference in the Debug Store (DS) feature flag; what use do you want to make of this information (the ProcessorId in its entirety or the Debug Store support flag in particular)?

Gary