__cpuid

Article
11/18/2006

Microsoft Specific

Generates the cpuid instruction available on x86 and x64, which queries the processor for information about the supported features and CPU type.

void __cpuid(
   int CPUInfo[4],
   int InfoType
);

Parameters

[out] CPUInfo
The information returned in an array of four integers.

[in] InfoType
A code indicating the type of information to be retrieved.

Requirements

Intrinsic	Architecture
__cpuid	x86, x64

Header file <intrin.h>

Remarks

The supported features and CPU type information is returned in CPUInfo, an array of four 32-bit integers that is filled with the values of the EAX, EBX, ECX, and EDX registers (in that order) after the cpuid instruction is called. The information returned has a different meaning depending on the value passed as the InfoType parameter. The information returned with various values of InfoType is processor-dependent.

When the InfoType argument is 0, the following table describes the output.

Information Returned

Array index	Bit range	Description
0	0-31	Maximum meaningful value for the InfoType parameter.
1	0-31	Identification String (part 1)
2	0-31	Identification String (part 3)
3	0-31	Identification String (part 2)

When the InfoType argument is 1, the following table describes the output.

CPU Information Returned

Array index	Bit range	Description
0	0-3	Stepping ID
0	4-7	Model
0	8-11	Family
0	12-13	Processor Type
0	14-15	Reserved
0	16-19	Extended model
0	20-27	Extended family
0	28-31	Reserved
1	0-7	Brand Index
1	8-15	CLFLUSH cache line size / 8
1	16-23	Reserved
1	24-31	APIC Physical ID
2	0	SSE3 New Instructions
2	1-2	Reserved
2	3	MONITOR/MWAIT
2	4	CPL Qualified Debug Store
2	5-7	Reserved
2	8	Thermal Monitor 2
2	9	Reserved
2	10	L1 Context ID
2	11-31	Reserved
3	0-31	Feature Information (see below)

The following table shows the meaning of the Feature Information value, the value of EDX which is written to CPUInfo[3], when the InfoType argument is 1.

Feature Information Returned

Bit	Mnemonic	Description
0	FPU	x87 FPU on Chip
1	VME	Virtual-8086 Mode Enhancement
2	DE	Debugging Extensions
3	PSE	Page Size Extensions
4	TSC	Time Stamp Counter
5	MSR	RDMSR and WRMSR Support
6	PAE	Physical Address Extensions
7	MCE	Machine Check Exception
8	CX8	CMPXCHG8B Inst.
9	APIC	APIC on Chip
10	n/a	Reserved
11	SEP	SYSENTER and SYSEXIT
12	MTRR	Memory Type Range Registers
13	PGE	PTE Global Bit
14	MCA	Machine Check Architecture
15	CMOV	Conditional Move/Compare Instruction
16	PAT	Page Attribute Table
17	PSE	Page Size Extension
18	PSN	Processor Serial Number
19	CLFSH	CFLUSH Instruction
20	n/a	Reserved
21	DS	Debug Store
22	ACPI	Thermal Monitor and Clock Ctrl
23	MMX	MMX Technology
24	FXSR	FXSAVE/FXRSTOR
25	SSE	SSE Extensions
26	SSE2	SSE2 Extensions
27	SS	Self Snoop
28	HTT	Hyper-threading technology
29	TM	Thermal Monitor
30	n/a	Reserved
31	PBE	Pend. Brk. En.

Some processors, such as the SSE3-enabled processors, support additional InfoType values. When the InfoType argument is 3 or 4, these processors might return cache and TLB information. When InfoType is 5, these processors return information relating to the monitor feature (see _mm_monitor).

The SSE3-enabled processors support Extended Function CPUID information. If this is supported, InfoType values from 0x8000000 might be used to return information. To determine the maximum meaningful value allowed, set InfoType to 0x8000000. The maximum value of InfoType supported will be written to CPUInfo[0]. The following table shows values returned using the extended function CPUID information.

Extended Function CPUID Information Returned

InfoType	Array index	Information
0x80000000	0	Maximum meaningful value of InfoType for extended function CPUID information.
0x80000000	1-3	Reserved.
0x80000001	0-4	Reserved
0x80000002	0-4	Processor Brand String
0x80000003	0-4	Processor Brand String, continued
0x80000004	0-4	Processor Brand String, continued
0x80000005	0-4	Reserved
0x80000006	0-1	Reserved
0x80000006	2	Bits 0-7: Cache Line Size Bits 12-15: L2 Associativity Bits 16-31: Cache size in 1K units
0x80000006	3	Reserved
0x80000007	0-4	Reserved

Example

// cpuid.cpp 
// processor: x86, x64
// Use the __cpuid intrinsic to get information about a CPU

#include <stdio.h>
#include <string.h>
#include <intrin.h>

const char* szFeatures[] =
{
    "x87 FPU On Chip",
    "Virtual-8086 Mode Enhancement",
    "Debugging Extensions",
    "Page Size Extensions",
    "Time Stamp Counter",
    "RDMSR and WRMSR Support",
    "Physical Address Extensions",
    "Machine Check Exception",
    "CMPXCHG8B Instruction",
    "APIC On Chip",
    "Unknown1",
    "SYSENTER and SYSEXIT",
    "Memory Type Range Registers",
    "PTE Global Bit",
    "Machine Check Architecture",
    "Conditional Move/Compare Instruction",
    "Page Attribute Table",
    "Page Size Extension",
    "Processor Serial Number",
    "CFLUSH Extension",
    "Unknown2",
    "Debug Store",
    "Thermal Monitor and Clock Ctrl",
    "MMX Technology",
    "FXSAVE/FXRSTOR",
    "SSE Extensions",
    "SSE2 Extensions",
    "Self Snoop",
    "Hyper-threading Technology",
    "Thermal Monitor",
    "Unknown4",
    "Pend. Brk. EN."
};

int main(int argc, char* argv[])
{
    char CPUString[0x20];
    char CPUBrandString[0x40];
    int CPUInfo[4] = {-1};
    int nSteppingID = 0;
    int nModel = 0;
    int nFamily = 0;
    int nProcessorType = 0;
    int nExtendedmodel = 0;
    int nExtendedfamily = 0;
    int nBrandIndex = 0;
    int nCLFLUSHcachelinesize = 0;
    int nAPICPhysicalID = 0;
    int nFeatureInfo = 0;
    int nCacheLineSize = 0;
    int nL2Associativity = 0;
    int nCacheSizeK = 0;
    int nRet = 0;
    unsigned    nIds, nExIds, i;
    bool    bSSE3NewInstructions = false;
    bool    bMONITOR_MWAIT = false;
    bool    bCPLQualifiedDebugStore = false;
    bool    bThermalMonitor2 = false;


    // __cpuid with an InfoType argument of 0 returns the number of
    // valid Ids in CPUInfo[0] and the CPU identification string in
    // the other three array elements. The CPU identification string is
    // not in linear order. The code below arranges the information 
    // in a human readable form.
    __cpuid(CPUInfo, 0);
    nIds = CPUInfo[0];
    memset(CPUString, 0, sizeof(CPUString));
    *((int*)CPUString) = CPUInfo[1];
    *((int*)(CPUString+4)) = CPUInfo[3];
    *((int*)(CPUString+8)) = CPUInfo[2];

    // Get the information associated with each valid Id
    for (i=0; i<=nIds; ++i)
    {
        __cpuid(CPUInfo, i);
        printf_s("\nFor InfoType %d\n", i); 
        printf_s("CPUInfo[0] = 0x%x\n", CPUInfo[0]);
        printf_s("CPUInfo[1] = 0x%x\n", CPUInfo[1]);
        printf_s("CPUInfo[2] = 0x%x\n", CPUInfo[2]);
        printf_s("CPUInfo[3] = 0x%x\n", CPUInfo[3]);

        // Interpret CPU feature information.
        if  (i == 1)
        {
            nSteppingID = CPUInfo[0] & 0xf;
            nModel = (CPUInfo[0] >> 4) & 0xf;
            nFamily = (CPUInfo[0] >> 8) & 0xf;
            nProcessorType = (CPUInfo[0] >> 12) & 0x3;
            nExtendedmodel = (CPUInfo[0] >> 16) & 0xf;
            nExtendedfamily = (CPUInfo[0] >> 20) & 0xff;
            nBrandIndex = CPUInfo[1] & 0xff;
            nCLFLUSHcachelinesize = ((CPUInfo[1] >> 8) & 0xff) * 8;
            nAPICPhysicalID = (CPUInfo[1] >> 24) & 0xff;
            bSSE3NewInstructions = (CPUInfo[2] & 0x1) || false;
            bMONITOR_MWAIT = (CPUInfo[2] & 0x8) || false;
            bCPLQualifiedDebugStore = (CPUInfo[2] & 0x10) || false;
            bThermalMonitor2 = (CPUInfo[2] & 0x100) || false;
            nFeatureInfo = CPUInfo[3];
        }
    }

    // Calling __cpuid with 0x80000000 as the InfoType argument
    // gets the number of valid extended IDs.
    __cpuid(CPUInfo, 0x80000000);
    nExIds = CPUInfo[0];
    memset(CPUBrandString, 0, sizeof(CPUBrandString));

    // Get the information associated with each extended ID.
    for (i=0x80000000; i<=nExIds; ++i)
    {
        __cpuid(CPUInfo, i);
        printf_s("\nFor InfoType %x\n", i); 
        printf_s("CPUInfo[0] = 0x%x\n", CPUInfo[0]);
        printf_s("CPUInfo[1] = 0x%x\n", CPUInfo[1]);
        printf_s("CPUInfo[2] = 0x%x\n", CPUInfo[2]);
        printf_s("CPUInfo[3] = 0x%x\n", CPUInfo[3]);

        // Interpret CPU brand string and cache information.
        if  (i == 0x80000002)
            memcpy(CPUBrandString, CPUInfo, sizeof(CPUInfo));
        else if  (i == 0x80000003)
            memcpy(CPUBrandString + 16, CPUInfo, sizeof(CPUInfo));
        else if  (i == 0x80000004)
            memcpy(CPUBrandString + 32, CPUInfo, sizeof(CPUInfo));
        else if  (i == 0x80000006)
        {
            nCacheLineSize = CPUInfo[2] & 0xff;
            nL2Associativity = (CPUInfo[2] >> 12) & 0xf;
            nCacheSizeK = (CPUInfo[2] >> 16) & 0xffff;
        }
    }

    // Display all the information in user-friendly format.

    printf_s("\n\nCPU String: %s\n", CPUString);

    if  (nIds >= 1)
    {
        if  (nSteppingID)
            printf_s("Stepping ID = %d\n", nSteppingID);
        if  (nModel)
            printf_s("Model = %d\n", nModel);
        if  (nFamily)
            printf_s("Family = %d\n", nFamily);
        if  (nProcessorType)
            printf_s("Processor Type = %d\n", nProcessorType);
        if  (nExtendedmodel)
            printf_s("Extended model = %d\n", nExtendedmodel);
        if  (nExtendedfamily)
            printf_s("Extended family = %d\n", nExtendedfamily);
        if  (nBrandIndex)
            printf_s("Brand Index = %d\n", nBrandIndex);
        if  (nCLFLUSHcachelinesize)
            printf_s("CLFLUSH cache line size = %d\n",
                     nCLFLUSHcachelinesize);
        if  (nAPICPhysicalID)
            printf_s("APIC Physical ID = %d\n", nAPICPhysicalID);

if  (nFeatureInfo || bSSE3NewInstructions ||
             bMONITOR_MWAIT || bCPLQualifiedDebugStore ||
             bThermalMonitor2)
        {
            printf_s("\nThe following features are supported:\n");

if  (bSSE3NewInstructions)
printf_s("\tSSE3 New Instructions\n");
if  (bMONITOR_MWAIT)
printf_s("\tMONITOR/MWAIT\n");
if  (bCPLQualifiedDebugStore)
printf_s("\tCPL Qualified Debug Store\n");
if  (bThermalMonitor2)
printf_s("\tThermal Monitor 2\n");

            i = 0;
            nIds = 1;
            while (i < (sizeof(szFeatures)/sizeof(const char*)))
            {
                if  (nFeatureInfo & nIds)
                {
                    printf_s("\t");
                    printf_s(szFeatures[i]);
                    printf_s("\n");
                }

                nIds <<= 1;
                ++i;
            }
        }
    }

    if  (nExIds >= 0x80000004)
        printf_s("\nCPU Brand String: %s\n", CPUBrandString);

    if  (nExIds >= 0x80000006)
    {
        printf_s("Cache Line Size = %d\n", nCacheLineSize);
        printf_s("L2 Associativity = %d\n", nL2Associativity);
        printf_s("Cache Size = %dK\n", nCacheSizeK);
    }

return  nRet;
}

Sample Output

For InfoType 0
CPUInfo[0] = 0x5
CPUInfo[1] = 0x756e6547
CPUInfo[2] = 0x6c65746e
CPUInfo[3] = 0x49656e69

For InfoType 1
CPUInfo[0] = 0xf31
CPUInfo[1] = 0x20800
CPUInfo[2] = 0x41d
CPUInfo[3] = 0xbfebfbff

For InfoType 2
CPUInfo[0] = 0x605b5001
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x7c7040

For InfoType 3
CPUInfo[0] = 0x0
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 4
CPUInfo[0] = 0x0
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 5
CPUInfo[0] = 0x40
CPUInfo[1] = 0x40
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 80000000
CPUInfo[0] = 0x80000008
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 80000001
CPUInfo[0] = 0x0
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 80000002
CPUInfo[0] = 0x20202020
CPUInfo[1] = 0x20202020
CPUInfo[2] = 0x20202020
CPUInfo[3] = 0x20202020

For InfoType 80000003
CPUInfo[0] = 0x47202020
CPUInfo[1] = 0x69756e65
CPUInfo[2] = 0x4920656e
CPUInfo[3] = 0x6c65746e

For InfoType 80000004
CPUInfo[0] = 0x20295228
CPUInfo[1] = 0x20555043
CPUInfo[2] = 0x30382e32
CPUInfo[3] = 0x7a4847

For InfoType 80000005
CPUInfo[0] = 0x0
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 80000006
CPUInfo[0] = 0x0
CPUInfo[1] = 0x0
CPUInfo[2] = 0x4008040
CPUInfo[3] = 0x0

For InfoType 80000007
CPUInfo[0] = 0x0
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0

For InfoType 80000008
CPUInfo[0] = 0x2028
CPUInfo[1] = 0x0
CPUInfo[2] = 0x0
CPUInfo[3] = 0x0


CPU String: GenuineIntel
Stepping ID = 1
Model = 3
Family = 15
CLFLUSH cache line size = 64

The following features are supported:
        SSE3 New Instructions
        MONITOR/MWAIT
        CPL Qualified Debug Store
        x87 FPU On Chip
        Virtual-8086 Mode Enhancement
        Debugging Extensions
        Page Size Extensions
        Time Stamp Counter
        RDMSR and WRMSR Support
        Physical Address Extensions
        Machine Check Exception
        CMPXCHG8B Instruction
        APIC On Chip
        SYSENTER and SYSEXIT
        Memory Type Range Registers
        PTE Global Bit
        Machine Check Architecture
        Conditional Move/Compare Instruction
        Page Attribute Table
        Page Size Extension
        CFLUSH Extension
        Debug Store
        Thermal Monitor and Clock Ctrl
        MMX Technology
        FXSAVE/FXRSTOR
        SSE Extensions
        SSE2 Extensions
        Self Snoop
        Hyper-threading Technology
        Thermal Monitor
        Pend. Brk. EN.

CPU Brand String:                    Genuine Intel(R) CPU 2.80GHz
Cache Line Size = 64
L2 Associativity = 8
Cache Size = 1024K

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__cpuid

Parameters

Requirements

Remarks

Example

Sample Output

END Microsoft Specific

See Also

Reference

Additional resources