CPUID—CPU Identification

Instruction Operand Encoding

Description

The ID flag (bit 21) in the EFLAGS register indicates support for the CPUID instruction. If a software procedure can set and clear this flag, the processor executing the procedure supports the CPUID instruction. This instruction oper-ates the same in non-64-bit modes and 64-bit mode.

CPUID returns processor identification and feature information in the EAX, EBX, ECX, and EDX registers.¹ The instruction’s output is dependent on the contents of the EAX register upon execution (in some cases, ECX as well). For example, the following pseudocode loads EAX with 00H and causes CPUID to return a Maximum Return Value and the Vendor Identification String in the appropriate registers:

MOV EAX, 00H

CPUID

Table 3-17 shows information returned, depending on the initial value loaded into the EAX register. Table 3-18 shows the maximum CPUID input value recognized for each family of IA-32 processors on which CPUID is imple-mented.

Two types of information are returned: basic and extended function information. If a value entered for CPUID.EAX is higher than the maximum input value for basic or extended function for that processor then the data for the highest basic information leaf is returned. For example, using the Intel Core i7 processor, the following is true:

CPUID.EAX = 05H (* Returns MONITOR/MWAIT leaf. *)

CPUID.EAX = 0AH (* Returns Architectural Performance Monitoring leaf. *)

CPUID.EAX = 0BH (* Returns Extended Topology Enumeration leaf. *)

CPUID.EAX = 0CH (* INVALID: Returns the same information as CPUID.EAX = 0BH. *)

CPUID.EAX = 80000008H (* Returns linear/physical address size data. *)

CPUID.EAX = 8000000AH (* INVALID: Returns same information as CPUID.EAX = 0BH. *)

If a value entered for CPUID.EAX is less than or equal to the maximum input value and the leaf is not supported on that processor then 0 is returned in all the registers. For example, using the Intel Core i7 processor, the following is true:

CPUID.EAX = 07H (*Returns EAX=EBX=ECX=EDX=0. *)

When CPUID returns the highest basic leaf information as a result of an invalid input EAX value, any dependence on input ECX value in the basic leaf is honored.

CPUID can be executed at any privilege level to serialize instruction execution. Serializing instruction execution guarantees that any modifications to flags, registers, and memory for previous instructions are completed before the next instruction is fetched and executed.

See also:

“Serializing Instructions” in Chapter 8, “Multiple-Processor Management,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A.

1.

On Intel 64 processors, CPUID clears the high 32 bits of the RAX/RBX/RCX/RDX registers in all modes.

“Caching Translation Information” in Chapter 4, “Paging,” in the Intel® 64 and IA-32 Architectures Software Devel-oper’s Manual, Volume 3A.

Table 3-17. Information Returned by CPUID Instruction

Initial EAX

Value

Information Provided about the Processor

Basic CPUID Information

0H

EAX

Maximum Input Value for Basic CPUID Information (see Table 3-18)

EBX

“Genu”

ECX

“ntel”

EDX

“ineI”

01H

EAX

Version Information: Type, Family, Model, and Stepping ID (see Figure 3-5)

EBX

Bits 07-00: Brand Index Bits 15-08: CLFLUSH line size (Value ∗ 8 = cache line size in bytes) Bits 23-16: Maximum number of addressable IDs for logical processors in this physical package*. Bits 31-24: Initial APIC ID

ECX

Feature Information (see Figure 3-6 and Table 3-20)

EDX

Feature Information (see Figure 3-7 and Table 3-21)

NOTES:

*

The nearest power-of-2 integer that is not smaller than EBX[23:16] is the number of unique initial APIC IDs reserved for addressing different logical processors in a physical package. This field is only valid if CPUID.1.EDX.HTT[bit 28]= 1.

02H

EAX

Cache and TLB Information (see Table 3-22)

EBX

Cache and TLB Information

ECX

Cache and TLB Information

EDX

Cache and TLB Information

03H

EAX

Reserved.

EBX

Reserved.

ECX

Bits 00-31 of 96 bit processor serial number. (Available in Pentium III processor only; otherwise, the value in this register is reserved.)

EDX

Bits 32-63 of 96 bit processor serial number. (Available in Pentium III processor only; otherwise, the value in this register is reserved.)

NOTES:

Processor serial number (PSN) is not supported in the Pentium 4 processor or later. On all models, use the PSN flag (returned using CPUID) to check for PSN support before accessing the feature.

See AP-485, Intel Processor Identification and the CPUID Instruction (Order Number 241618) for more information on PSN.

CPUID leaves > 3 < 80000000 are visible only when IA32_MISC_ENABLE.BOOT_NT4[bit 22] = 0 (default).

Deterministic Cache Parameters Leaf

NOTES:

04H

Leaf 04H output depends on the initial value in ECX.*

See also: “INPUT EAX = 4: Returns Deterministic Cache Parameters for each level on page 3-182.

EAX

Bits 04-00: Cache Type Field

0 = Null - No more caches 1 = Data Cache 2 = Instruction Cache 3 = Unified Cache 4-31 = Reserved

Table 3-17. Information Returned by CPUID Instruction (Contd.)

NOTES:

* If ECX contains an invalid sub leaf index, EAX/EBX/ECX/EDX return 0. Sub-leaf index n+1 is invalid if sub-

leaf n returns EAX[4:0] as 0.

** Add one to the return value to get the result.

***The nearest power-of-2 integer that is not smaller than (1 + EAX[25:14]) is the number of unique ini-

tial APIC IDs reserved for addressing different logical processors sharing this cache

**** The nearest power-of-2 integer that is not smaller than (1 + EAX[31:26]) is the number of unique

Core_IDs reserved for addressing different processor cores in a physical package. Core ID is a subset of bits of the initial APIC ID.

***** The returned value is constant for valid initial values in ECX. Valid ECX values start from 0.

MONITOR/MWAIT Leaf

05H

EAX

Bits 15-00: Smallest monitor-line size in bytes (default is processor's monitor granularity) Bits 31-16: Reserved = 0

EBX

Bits 15-00: Largest monitor-line size in bytes (default is processor's monitor granularity) Bits 31-16: Reserved = 0

ECX

Bit 00: Enumeration of Monitor-Mwait extensions (beyond EAX and EBX registers) supported

Bit 01: Supports treating interrupts as break-event for MWAIT, even when interrupts disabled

Bits 31 - 02: Reserved

Table 3-17. Information Returned by CPUID Instruction (Contd.)

Table 3-17. Information Returned by CPUID Instruction (Contd.)

Table 3-17. Information Returned by CPUID Instruction (Contd.)

NOTES:

0BH

Most of Leaf 0BH output depends on the initial value in ECX.

The EDX output of leaf 0BH is always valid and does not vary with input value in ECX.

Output value in ECX[7:0] always equals input value in ECX[7:0].

For sub-leaves that return an invalid level-type of 0 in ECX[15:8]; EAX and EBX will return 0.

If an input value n in ECX returns the invalid level-type of 0 in ECX[15:8], other input values with ECX >

n also return 0 in ECX[15:8].

EAX

Bits 04-00: Number of bits to shift right on x2APIC ID to get a unique topology ID of the next level type*. All logical processors with the same next level ID share current level. Bits 31-05: Reserved.

EBX

Bits 15 - 00: Number of logical processors at this level type. The number reflects configuration as shipped by Intel**. Bits 31- 16: Reserved.

ECX

Bits 07 - 00: Level number. Same value in ECX input Bits 15 - 08: Level type***. Bits 31 - 16:: Reserved.

EDX

Bits 31- 00: x2APIC ID the current logical processor.

NOTES: * Software should use this field (EAX[4:0]) to enumerate processor topology of the system.

** Software must not use EBX[15:0] to enumerate processor topology of the system. This value in this field (EBX[15:0]) is only intended for display/diagnostic purposes. The actual number of logical processors available to BIOS/OS/Applications may be different from the value of EBX[15:0], depending on software and platform hardware configurations.

*** The value of the “level type” field is not related to level numbers in any way, higher “level type” val-ues do not mean higher levels. Level type field has the following encoding: 0 : invalid 1 : SMT 2 : Core 3-255 : Reserved

Processor Extended State Enumeration Main Leaf (EAX = 0DH, ECX = 0)

NOTES:

0DH

Leaf 0DH main leaf (ECX = 0).

EAX

Bits 31-00: Reports the valid bit fields of the lower 32 bits of XCR0. If a bit is 0, the corresponding bit field in XCR0 is reserved. Bit 00: legacy x87 Bit 01: 128-bit SSE Bit 02: 256-bit AVX Bits 31- 03: Reserved

EBX

Bits 31-00: Maximum size (bytes, from the beginning of the XSAVE/XRSTOR save area) required by enabled features in XCR0. May be different than ECX if some features at the end of the XSAVE save area are not enabled.

Table 3-17. Information Returned by CPUID Instruction (Contd.)

NOTES:

0DH

Leaf 0DH output depends on the initial value in ECX.

Each valid sub-leaf index maps to a valid bit in either the XCR0 register or the IA32_XSS MSR starting at bit position 2.

* If ECX contains an invalid sub-leaf index, EAX/EBX/ECX/EDX return 0. Sub-leaf n (0 ≤ n ≤ 31) is invalid

if sub-leaf 0 returns 0 in EAX[n] and sub-leaf 1 returns 0 in ECX[n]. Sub-leaf n (32 ≤ n ≤ 63) is invalid if sub-leaf 0 returns 0 in EDX[n-32] and sub-leaf 1 returns 0 in EDX[n-32].

EAX

Bits 31-0: The size in bytes (from the offset specified in EBX) of the save area for an extended state fea-ture associated with a valid sub-leaf index, n.

EBX

Bits 31-0: The offset in bytes of this extended state component’s save area from the beginning of the XSAVE/XRSTOR area. This field reports 0 if the sub-leaf index, n, does not map to a valid bit in the XCR0 register*.

ECX

Bit 0 is set if the sub-leaf index, n, maps to a valid bit in the IA32_XSS MSR and bit 0 is clear if n maps to a valid bit in XCR0. Bits 31-1 are reserved. This field reports 0 if the sub-leaf index, n, is invalid*.

EDX

This field reports 0 if the sub-leaf index, n, is invalid*; otherwise it is reserved.

Platform QoS Monitoring Enumeration Sub-leaf (EAX = 0FH, ECX = 0)

NOTES:

0FH

Leaf 0FH output depends on the initial value in ECX.

Sub-leaf index 0 reports valid resource type starting at bit position 1 of EDX

EAX

Reserved.

EBX

Bits 31-0: Maximum range (zero-based) of RMID within this physical processor of all types.

ECX

Reserved.

Table 3-17. Information Returned by CPUID Instruction (Contd.)

NOTES:

0FH

Leaf 0FH output depends on the initial value in ECX.

EAX

Reserved.

EBX

Bits 31-0: Conversion factor from reported IA32_QM_CTR value to occupancy metric (bytes).

ECX

Maximum range (zero-based) of RMID of this resource type.

EDX

Bit 00: Supports L3 occupancy monitoring if 1. Bits 31:01: Reserved

Platform QoS Enforcement Enumeration Sub-leaf (EAX = 10H, ECX = 0)

NOTES:

10H

Leaf 10H output depends on the initial value in ECX.

Sub-leaf index 0 reports valid resource identification (ResID) starting at bit position 1 of EDX

EAX

Reserved.

EBX

Bit 00: Reserved. Bit 01: Supports L3 Cache QoS Enforcement if 1. Bits 31:02: Reserved

ECX

Reserved.

EDX

Reserved.

L3 Cache QoS Enforcement Enumeration Sub-leaf (EAX = 10H, ECX = ResID =1)

NOTES:

10H

Leaf 10H output depends on the initial value in ECX.

EAX

Bits 4:0: Length of the capacity bit mask for the corresponding ResID. Bits 31:05: Reserved

EBX

Bits 31-0: Bit-granular map of isolation/contention of allocation units.

ECX

Bit 00: Reserved. Bit 01: Updates of COS should be infrequent if 1. Bits 31:02: Reserved

EDX

Bits 15:0: Highest COS number supported for this ResID. Bits 31:16: Reserved

Intel Processor Trace Enumeration Main Leaf (EAX = 14H, ECX = 0)

NOTES:

14H

Leaf 14H main leaf (ECX = 0).

EAX

Bits 31-0: Reports the maximum number sub-leaves that are supported in leaf 14H.

EBX

Bit 00: If 1, Indicates that IA32_RTIT_CTL.CR3Filter can be set to 1, and that IA32_RTIT_CR3_MATCH MSR can be accessed. Bits 31- 01: Reserved

Table 3-17. Information Returned by CPUID Instruction (Contd.)

Table 3-17. Information Returned by CPUID Instruction (Contd.)

NOTES:

* L2 associativity field encodings:

00H - Disabled 01H - Direct mapped 02H - 2-way 04H - 4-way 06H - 8-way 08H - 16-way 0FH - Fully associative

80000007H

EAX

Reserved = 0

EBX

Reserved = 0

ECX

Reserved = 0

EDX

Bits 07-00: Reserved = 0 Bit 08: Invariant TSC available if 1 Bits 31-09: Reserved = 0

80000008H

EAX

Linear/Physical Address size Bits 07-00: #Physical Address Bits* Bits 15-8: #Linear Address Bits Bits 31-16: Reserved = 0

EBX

Reserved = 0

ECX

Reserved = 0

EDX

Reserved = 0

NOTES:

*

If CPUID.80000008H:EAX[7:0] is supported, the maximum physical address number supported should come from this field.

INPUT EAX = 0: Returns CPUID’s Highest Value for Basic Processor Information and the Vendor Identification String

When CPUID executes with EAX set to 0, the processor returns the highest value the CPUID recognizes for returning basic processor information. The value is returned in the EAX register (see Table 3-18) and is processor specific.

A vendor identification string is also returned in EBX, EDX, and ECX. For Intel processors, the string is “Genuin-

eIntel” and is expressed:

EBX ← 756e6547h (* "Genu", with G in the low eight bits of BL *)

EDX ← 49656e69h (* "ineI", with i in the low eight bits of DL *)

ECX ← 6c65746eh (* "ntel", with n in the low eight bits of CL *)

INPUT EAX = 80000000H: Returns CPUID’s Highest Value for Extended Processor Information

When CPUID executes with EAX set to 80000000H, the processor returns the highest value the processor recog-nizes for returning extended processor information. The value is returned in the EAX register (see Table 3-18) and is processor specific.

Table 3-18. Highest CPUID Source Operand for Intel 64 and IA-32 Processors

IA32_BIOS_SIGN_ID Returns Microcode Update Signature

For processors that support the microcode update facility, the IA32_BIOS_SIGN_ID MSR is loaded with the update signature whenever CPUID executes. The signature is returned in the upper DWORD. For details, see Chapter 9 in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A.

INPUT EAX = 1: Returns Model, Family, Stepping Information

When CPUID executes with EAX set to 1, version information is returned in EAX (see Figure 3-5). For example: model, family, and processor type for the Intel Xeon processor 5100 series is as follows:

See Table 3-19 for available processor type values. Stepping IDs are provided as needed.

Figure 3-5. Version Information Returned by CPUID in EAX

Table 3-19. Processor Type Field

NOTE

See Chapter 17 in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1, for information on identifying earlier IA-32 processors.

The Extended Family ID needs to be examined only when the Family ID is 0FH. Integrate the fields into a display using the following rule:

IF Family_ID ≠ 0FH

THEN DisplayFamily = Family_ID;

ELSE DisplayFamily = Extended_Family_ID + Family_ID;

(* Right justify and zero-extend 4-bit field. *)

FI;

(* Show DisplayFamily as HEX field. *)

The Extended Model ID needs to be examined only when the Family ID is 06H or 0FH. Integrate the field into a display using the following rule:

IF (Family_ID = 06H or Family_ID = 0FH)

THEN DisplayModel = (Extended_Model_ID « 4) + Model_ID;

(* Right justify and zero-extend 4-bit field; display Model_ID as HEX field.*)

ELSE DisplayModel = Model_ID;

FI;

(* Show DisplayModel as HEX field. *)

INPUT EAX = 1: Returns Additional Information in EBX

When CPUID executes with EAX set to 1, additional information is returned to the EBX register:

INPUT EAX = 1: Returns Feature Information in ECX and EDX

When CPUID executes with EAX set to 1, feature information is returned in ECX and EDX.

For all feature flags, a 1 indicates that the feature is supported. Use Intel to properly interpret feature flags.

NOTE

Software must confirm that a processor feature is present using feature flags returned by CPUID prior to using the feature. Software should not depend on future offerings retaining all features.

Figure 3-6. Feature Information Returned in the ECX Register

Table 3-20. Feature Information Returned in the ECX Register

Bit #

Mnemonic

Description

Streaming SIMD Extensions 3 (SSE3). A value of 1 indicates the processor supports this

0

SSE3

technology.

PCLMULQDQ. A value of 1 indicates the processor supports the PCLMULQDQ instruction.

1

PCLMULQDQ

64-bit DS Area. A value of 1 indicates the processor supports DS area using 64-bit layout.

2

DTES64

MONITOR/MWAIT. A value of 1 indicates the processor supports this feature.

3

MONITOR

CPL Qualified Debug Store. A value of 1 indicates the processor supports the extensions to the

4

DS-CPL

Debug Store feature to allow for branch message storage qualified by CPL.

Virtual Machine Extensions. A value of 1 indicates that the processor supports this technology.

5

VMX

Safer Mode Extensions. A value of 1 indicates that the processor supports this technology. See

6

SMX

Chapter 5, “Safer Mode Extensions Reference”.

Enhanced Intel SpeedStep® technology. A value of 1 indicates that the processor supports this

7

EIST

technology.

Thermal Monitor 2. A value of 1 indicates whether the processor supports this technology.

8

TM2

9

SSSE3

A value of 1 indicates the presence of the Supplemental Streaming SIMD Extensions 3 (SSSE3). A value of 0 indicates the instruction extensions are not present in the processor.

L1 Context ID. A value of 1 indicates the L1 data cache mode can be set to either adaptive mode

10

CNXT-ID

or shared mode. A value of 0 indicates this feature is not supported. See definition of the IA32_MISC_ENABLE MSR Bit 24 (L1 Data Cache Context Mode) for details.

11

SDBG

A value of 1 indicates the processor supports IA32_DEBUG_INTERFACE MSR for silicon debug.

12

FMA

A value of 1 indicates the processor supports FMA extensions using YMM state.

CMPXCHG16B Available. A value of 1 indicates that the feature is available. See the

13

CMPXCHG16B

“CMPXCHG8B/CMPXCHG16B—Compare and Exchange Bytes” section in this chapter for a description.

xTPR Update Control. A value of 1 indicates that the processor supports changing

14

xTPR Update Control

IA32_MISC_ENABLE[bit 23].

Perfmon and Debug Capability: A value of 1 indicates the processor supports the performance

15

PDCM

and debug feature indication MSR IA32_PERF_CAPABILITIES.

16

Reserved

Reserved

Process-context identifiers. A value of 1 indicates that the processor supports PCIDs and that

17

PCID

software may set CR4.PCIDE to 1.

18

DCA

A value of 1 indicates the processor supports the ability to prefetch data from a memory mapped device.

19

SSE4.1

A value of 1 indicates that the processor supports SSE4.1.

20

SSE4.2

A value of 1 indicates that the processor supports SSE4.2.

21

x2APIC

A value of 1 indicates that the processor supports x2APIC feature.

22

MOVBE

A value of 1 indicates that the processor supports MOVBE instruction.

23

POPCNT

A value of 1 indicates that the processor supports the POPCNT instruction.

24

TSC-Deadline

A value of 1 indicates that the processor’s local APIC timer supports one-shot operation using a TSC deadline value.

25

AESNI

A value of 1 indicates that the processor supports the AESNI instruction extensions.

26

XSAVE

A value of 1 indicates that the processor supports the XSAVE/XRSTOR processor extended states feature, the XSETBV/XGETBV instructions, and XCR0.

27

OSXSAVE

A value of 1 indicates that the OS has set CR4.OSXSAVE[bit 18] to enable the XSAVE feature set.

28

AVX

A value of 1 indicates the processor supports the AVX instruction extensions.

Table 3-20. Feature Information Returned in the ECX Register (Contd.)

Bit #

Mnemonic

Description

29

F16C

A value of 1 indicates that processor supports 16-bit floating-point conversion instructions.

30

RDRAND

A value of 1 indicates that processor supports RDRAND instruction.

31

Not Used

Always returns 0.

Figure 3-7. Feature Information Returned in the EDX Register

Table 3-21. More on Feature Information Returned in the EDX Register

Table 3-21. More on Feature Information Returned in the EDX Register (Contd.)

INPUT EAX = 2: TLB/Cache/Prefetch Information Returned in EAX, EBX, ECX, EDX

When CPUID executes with EAX set to 2, the processor returns information about the processor’s internal TLBs, cache and prefetch hardware in the EAX, EBX, ECX, and EDX registers. The information is reported in encoded form and fall into the following categories:

Table 3-22. Encoding of CPUID Leaf 2 Descriptors

Table 3-22. Encoding of CPUID Leaf 2 Descriptors (Contd.)

Table 3-22. Encoding of CPUID Leaf 2 Descriptors (Contd.)

Example 3-1. Example of Cache and TLB Interpretation

The first member of the family of Pentium 4 processors returns the following information about caches and TLBs when the CPUID executes with an input value of 2:

EAX

66 5B 50 01H

EBX

0H

ECX

0H

EDX

00 7A 70 00H

Which means:

— 50H - a 64-entry instruction TLB, for mapping 4-KByte and 2-MByte or 4-MByte pages.

— 5BH - a 64-entry data TLB, for mapping 4-KByte and 4-MByte pages.

— 66H - an 8-KByte 1st level data cache, 4-way set associative, with a 64-Byte cache line size.

— 00H - NULL descriptor.

— 70H - Trace cache: 12 K-µop, 8-way set associative.

— 7AH - a 256-KByte 2nd level cache, 8-way set associative, with a sectored, 64-byte cache line size.

— 00H - NULL descriptor.

INPUT EAX = 04H: Returns Deterministic Cache Parameters for Each Level

When CPUID executes with EAX set to 04H and ECX contains an index value, the processor returns encoded data that describe a set of deterministic cache parameters (for the cache level associated with the input in ECX). Valid index values start from 0.

Software can enumerate the deterministic cache parameters for each level of the cache hierarchy starting with an index value of 0, until the parameters report the value associated with the cache type field is 0. The architecturally defined fields reported by deterministic cache parameters are documented in Table 3-17.

This Cache Size in Bytes

= (Ways + 1) * (Partitions + 1) * (Line_Size + 1) * (Sets + 1)

= (EBX[31:22] + 1) * (EBX[21:12] + 1) * (EBX[11:0] + 1) * (ECX + 1)

The CPUID leaf 04H also reports data that can be used to derive the topology of processor cores in a physical package. This information is constant for all valid index values. Software can query the raw data reported by executing CPUID with EAX=04H and ECX=0 and use it as part of the topology enumeration algorithm described in Chapter 8, “Multiple-Processor Management,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A.

INPUT EAX = 05H: Returns MONITOR and MWAIT Features

When CPUID executes with EAX set to 05H, the processor returns information about features available to MONITOR/MWAIT instructions. The MONITOR instruction is used for address-range monitoring in conjunction with MWAIT instruction. The MWAIT instruction optionally provides additional extensions for advanced power manage-ment. See Table 3-17.

INPUT EAX = 06H: Returns Thermal and Power Management Features

When CPUID executes with EAX set to 06H, the processor returns information about thermal and power manage-ment features. See Table 3-17.

INPUT EAX = 07H: Returns Structured Extended Feature Enumeration Information

When CPUID executes with EAX set to 07H and ECX = 0, the processor returns information about the maximum input value for sub-leaves that contain extended feature flags. See Table 3-17.

When CPUID executes with EAX set to 07H and the input value of ECX is invalid (see leaf 07H entry in Table 3-17), the processor returns 0 in EAX/EBX/ECX/EDX. In subleaf 0, EAX returns the maximum input value of the highest leaf 7 sub-leaf, and EBX, ECX & EDX contain information of extended feature flags.

INPUT EAX = 09H: Returns Direct Cache Access Information

When CPUID executes with EAX set to 09H, the processor returns information about Direct Cache Access capabili-ties. See Table 3-17.

INPUT EAX = 0AH: Returns Architectural Performance Monitoring Features

When CPUID executes with EAX set to 0AH, the processor returns information about support for architectural performance monitoring capabilities. Architectural performance monitoring is supported if the version ID (see Table 3-17) is greater than Pn 0. See Table 3-17.

For each version of architectural performance monitoring capability, software must enumerate this leaf to discover the programming facilities and the architectural performance events available in the processor. The details are described in Chapter 23, “Introduction to Virtual-Machine Extensions,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3C.

INPUT EAX = 0BH: Returns Extended Topology Information

When CPUID executes with EAX set to 0BH, the processor returns information about extended topology enumera-tion data. Software must detect the presence of CPUID leaf 0BH by verifying (a) the highest leaf index supported by CPUID is >= 0BH, and (b) CPUID.0BH:EBX[15:0] reports a non-zero value. See Table 3-17.

INPUT EAX = 0DH: Returns Processor Extended States Enumeration Information

When CPUID executes with EAX set to 0DH and ECX = 0, the processor returns information about the bit-vector representation of all processor state extensions that are supported in the processor and storage size requirements of the XSAVE/XRSTOR area. See Table 3-17.

When CPUID executes with EAX set to 0DH and ECX = n (n > 1, and is a valid sub-leaf index), the processor returns information about the size and offset of each processor extended state save area within the XSAVE/XRSTOR area. See Table 3-17. Software can use the forward-extendable technique depicted below to query the valid sub-leaves and obtain size and offset information for each processor extended state save area:

For i = 2 to 62 // sub-leaf 1 is reserved

IF (CPUID.(EAX=0DH, ECX=0):VECTOR[i] = 1 ) // VECTOR is the 64-bit value of EDX:EAX

Execute CPUID.(EAX=0DH, ECX = i) to examine size and offset for sub-leaf i;

FI;

INPUT EAX = 0FH: Returns Platform Quality of Service (PQoS) Monitoring Enumeration Information

When CPUID executes with EAX set to 0FH and ECX = 0, the processor returns information about the bit-vector representation of QoS monitoring resource types that are supported in the processor and maximum range of RMID values the processor can use to monitor of any supported resource types. Each bit, starting from bit 1, corresponds to a specific resource type if the bit is set. The bit position corresponds to the sub-leaf index (or ResID) that soft-ware must use to query QoS monitoring capability available for that type. See Table 3-17.

When CPUID executes with EAX set to 0FH and ECX = n (n >= 1, and is a valid ResID), the processor returns infor-mation software can use to program IA32_PQR_ASSOC, IA32_QM_EVTSEL MSRs before reading QoS data from the IA32_QM_CTR MSR.

INPUT EAX = 10H: Returns Platform Quality of Service (PQoS) Enforcement Enumeration Information

When CPUID executes with EAX set to 10H and ECX = 0, the processor returns information about the bit-vector representation of QoS Enforcement resource types that are supported in the processor. Each bit, starting from bit 1, corresponds to a specific resource type if the bit is set. The bit position corresponds to the sub-leaf index (or ResID) that software must use to query QoS enforcement capability available for that type. See Table 3-17.

When CPUID executes with EAX set to 10H and ECX = n (n >= 1, and is a valid ResID), the processor returns infor-mation about available classes of service and range of QoS mask MSRs that software can use to configure each class of services using capability bit masks in the QoS Mask registers, IA32_resourceType_Mask_n.

METHODS FOR RETURNING BRANDING INFORMATION

Use the following techniques to access branding information:

1.

Processor brand string method.

2.

Processor brand index; this method uses a software supplied brand string table.

These two methods are discussed in the following sections. For methods that are available in early processors, see Section: “Identification of Earlier IA-32 Processors” in Chapter 17 of the Intel® 64 and IA-32 Architectures Soft-ware Developer’s Manual, Volume 1.

The Processor Brand String Method

Figure 3-8 describes the algorithm used for detection of the brand string. Processor brand identification software should execute this algorithm on all Intel 64 and IA-32 processors.

This method (introduced with Pentium 4 processors) returns an ASCII brand identification string and the Processor Base frequency of the processor to the EAX, EBX, ECX, and EDX registers.

Figure 3-8. Determination of Support for the Processor Brand String

How Brand Strings Work

To use the brand string method, execute CPUID with EAX input of 8000002H through 80000004H. For each input value, CPUID returns 16 ASCII characters using EAX, EBX, ECX, and EDX. The returned string will be NULL-termi-nated.

Table 3-23 shows the brand string that is returned by the first processor in the Pentium 4 processor family.

Table 3-23. Processor Brand String Returned with Pentium 4 Processor

Extracting the Processor Frequency from Brand Strings

Figure 3-9 provides an algorithm which software can use to extract the Processor Base frequency from the processor brand string.

Figure 3-9. Algorithm for Extracting Processor Frequency

The Processor Brand Index Method

The brand index method (introduced with Pentium^® III Xeon^® processors) provides an entry point into a brand identification table that is maintained in memory by system software and is accessible from system- and user-level code. In this table, each brand index is associate with an ASCII brand identification string that identifies the official Intel family and model number of a processor.

When CPUID executes with EAX set to 1, the processor returns a brand index to the low byte in EBX. Software can then use this index to locate the brand identification string for the processor in the brand identification table. The first entry (brand index 0) in this table is reserved, allowing for backward compatibility with processors that do not support the brand identification feature. Starting with processor signature family ID = 0FH, model = 03H, brand index method is no longer supported. Use brand string method instead.

Table 3-24 shows brand indices that have identification strings associated with them.

Table 3-24. Mapping of Brand Indices; and Intel 64 and IA-32 Processor Brand Strings

NOTES:

1.

Indicates versions of these processors that were introduced after the Pentium III

IA-32 Architecture Compatibility

CPUID is not supported in early models of the Intel486 processor or in any IA-32 processor earlier than the Intel486 processor.

Operation

IA32_BIOS_SIGN_ID MSR ← Update with installed microcode revision number;
CASE (EAX) OF
    EAX = 0:
         EAX ← Highest basic function input value understood by CPUID;
         EBX ← Vendor identification string;
         EDX ← Vendor identification string;
         ECX ← Vendor identification string;
    BREAK;
    EAX = 1H:
         EAX[3:0] ← Stepping ID;
         EAX[7:4] ← Model;
         EAX[11:8] ← Family;
         EAX[13:12] ← Processor type;
         EAX[15:14] ← Reserved;
         EAX[19:16] ← Extended Model;
         EAX[27:20] ← Extended Family;
         EAX[31:28] ← Reserved;
         EBX[7:0] ← Brand Index; (* Reserved if the value is zero. *)
         EBX[15:8] ← CLFLUSH Line Size;
         EBX[16:23] ← Reserved; (* Number of threads enabled = 2 if MT enable fuse set. *)
         EBX[24:31] ← Initial APIC ID;
         ECX ← Feature flags; (* See Figure 3-6. *)
         EDX ← Feature flags; (* See Figure 3-7. *)
    BREAK;
    EAX = 2H:
         EAX ← Cache and TLB information;
         EBX ← Cache and TLB information;
         ECX ← Cache and TLB information;
         EDX ← Cache and TLB information;
    BREAK;
    EAX = 3H:
         EAX ← Reserved;
         EBX ← Reserved;
         ECX ← ProcessorSerialNumber[31:0];
         (* Pentium III processors only, otherwise reserved. *)
         EDX ← ProcessorSerialNumber[63:32];
         (* Pentium III processors only, otherwise reserved. *
    BREAK
    EAX = 4H:
         EAX ← Deterministic Cache Parameters Leaf; (* See Table 3-17. *)
         EBX ← Deterministic Cache Parameters Leaf;
         ECX ← Deterministic Cache Parameters Leaf;
         EDX ← Deterministic Cache Parameters Leaf;
    BREAK;
    EAX = 5H:
         EAX ← MONITOR/MWAIT Leaf; (* See Table 3-17. *)
         EBX ← MONITOR/MWAIT Leaf;
         ECX ← MONITOR/MWAIT Leaf;
         EDX ← MONITOR/MWAIT Leaf;
    BREAK;
    EAX = 6H:
         EAX ← Thermal and Power Management Leaf; (* See Table 3-17. *)
         EBX ← Thermal and Power Management Leaf;
         ECX ← Thermal and Power Management Leaf;
         EDX ← Thermal and Power Management Leaf;
    BREAK;
    EAX = 7H:
         EAX ← Structured Extended Feature Flags Enumeration Leaf; (* See Table 3-17. *)
         EBX ← Structured Extended Feature Flags Enumeration Leaf;
         ECX ← Structured Extended Feature Flags Enumeration Leaf;
         EDX ← Structured Extended Feature Flags Enumeration Leaf;
    BREAK;
    EAX = 8H:
         EAX ← Reserved = 0;
         EBX ← Reserved = 0;
         ECX ← Reserved = 0;
         EDX ← Reserved = 0;
    BREAK;
    EAX = 9H:
         EAX ← Direct Cache Access Information Leaf; (* See Table 3-17. *)
         EBX ← Direct Cache Access Information Leaf;
         ECX ← Direct Cache Access Information Leaf;
         EDX ← Direct Cache Access Information Leaf;
    BREAK;
    EAX = AH:
         EAX ← Architectural Performance Monitoring Leaf; (* See Table 3-17. *)
         EBX ← Architectural Performance Monitoring Leaf;
         ECX ← Architectural Performance Monitoring Leaf;
         EDX ← Architectural Performance Monitoring Leaf;
         BREAK
    EAX = BH:
         EAX ← Extended Topology Enumeration Leaf; (* See Table 3-17. *)
         EBX ← Extended Topology Enumeration Leaf;
         ECX ← Extended Topology Enumeration Leaf;
         EDX ← Extended Topology Enumeration Leaf;
    BREAK;
    EAX = CH:
         EAX ← Reserved = 0;
         EBX ← Reserved = 0;
         ECX ← Reserved = 0;
         EDX ← Reserved = 0;
    BREAK;
    EAX = DH:
         EAX ← Processor Extended State Enumeration Leaf; (* See Table 3-17. *)
         EBX ← Processor Extended State Enumeration Leaf;
         ECX ← Processor Extended State Enumeration Leaf;
         EDX ← Processor Extended State Enumeration Leaf;
    BREAK;
    EAX = EH:
         EAX ← Reserved = 0;
         EBX ← Reserved = 0;
         ECX ← Reserved = 0;
         EDX ← Reserved = 0;
    BREAK;
    EAX = FH:
         EAX ← Platform Quality of Service Monitoring Enumeration Leaf; (* See Table 3-17. *)
         EBX ← Platform Quality of Service Monitoring Enumeration Leaf;
         ECX ← Platform Quality of Service Monitoring Enumeration Leaf;
         EDX ← Platform Quality of Service Monitoring Enumeration Leaf;
    BREAK;
    EAX = 10H:
         EAX ← Platform Quality of Service Enforcement Enumeration Leaf; (* See Table 3-17. *)
         EBX ← Platform Quality of Service Enforcement Enumeration Leaf;
         ECX ← Platform Quality of Service Enforcement Enumeration Leaf;
         EDX ← Platform Quality of Service Enforcement Enumeration Leaf;
    BREAK;
BREAK;
    EAX = 80000000H:
         EAX ← Highest extended function input value understood by CPUID;
         EBX ← Reserved;
         ECX ← Reserved;
         EDX ← Reserved;
    BREAK;
    EAX = 80000001H:
         EAX ← Reserved;
         EBX ← Reserved;
         ECX ← Extended Feature Bits (* See Table 3-17.*);
         EDX ← Extended Feature Bits (* See Table 3-17. *);
    BREAK;
    EAX = 80000002H:
         EAX ← Processor Brand String;
         EBX ← Processor Brand String, continued;
         ECX ← Processor Brand String, continued;
         EDX ← Processor Brand String, continued;
    BREAK;
    EAX = 80000003H:
         EAX ← Processor Brand String, continued;
         EBX ← Processor Brand String, continued;
         ECX ← Processor Brand String, continued;
         EDX ← Processor Brand String, continued;
    BREAK;
    EAX = 80000004H:
         EAX ← Processor Brand String, continued;
         EBX ← Processor Brand String, continued;
         ECX ← Processor Brand String, continued;
         EDX ← Processor Brand String, continued;
    BREAK;
    EAX = 80000005H:
         EAX ← Reserved = 0;
         EBX ← Reserved = 0;
         ECX ← Reserved = 0;
         EDX ← Reserved = 0;
    BREAK;
    EAX = 80000006H:
         EAX ← Reserved = 0;
         EBX ← Reserved = 0;
         ECX ← Cache information;
         EDX ← Reserved = 0;
    BREAK;
    EAX = 80000007H:
         EAX ← Reserved = 0;
         EBX ← Reserved = 0;
         ECX ← Reserved = 0;
         EDX ← Reserved = Misc Feature Flags;
    BREAK;
    EAX = 80000008H:
         EAX ← Reserved = Physical Address Size Information;
         EBX ← Reserved = Virtual Address Size Information;
         ECX ← Reserved = 0;
         EDX ← Reserved = 0;
    BREAK;
    EAX >= 40000000H and EAX <= 4FFFFFFFH:
    DEFAULT: (* EAX = Value outside of recognized range for CPUID. *)
         (* If the highest basic information leaf data depend on ECX input value, ECX is honored.*)
         EAX ← Reserved; (* Information returned for highest basic information leaf. *)
         EBX ← Reserved; (* Information returned for highest basic information leaf. *)
         ECX ← Reserved; (* Information returned for highest basic information leaf. *)
         EDX ← Reserved; (* Information returned for highest basic information leaf. *)
    BREAK;
ESAC;

Flags Affected

None.

Exceptions (All Operating Modes)

#UD

If the LOCK prefix is used.

In earlier IA-32 processors that do not support the CPUID instruction, execution of the instruc-tion results in an invalid opcode (#UD) exception being generated.