cpuid [leaf number]

Retrieve CPUID information from the processor. See The documentation of CPUID for more information.

CPUID Leaf Values

Leaf (EAX)	Sub-Leaf (ECX)	Purpose / Description	Example Outputs or Notes
0	-	Highest Standard Function and Vendor ID String. Returns the maximum supported standard leaf in EAX, and the vendor string across EBX, EDX, and ECX.	Example vendor strings: "GenuineIntel", "AuthenticAMD".
1	-	Processor Information and Feature Bits. Reports family, model, stepping, and feature flags such as SSE, AVX, FPU, MMX, etc.	EAX: version info; EBX: logical cores; ECX/EDX: feature flags.
2	-	Cache and TLB Descriptor Information. Legacy format describing cache/TLB layout. Superseded by leaf 4.	Used on older Intel CPUs.
3	-	Processor Serial Number. Deprecated and often disabled for privacy reasons.	Rarely supported.
4	n (0… until type=0)	Deterministic Cache Parameters. Reports cache level, type, line size, associativity, and set count.	Iterate ECX from 0 until EAX[bits 4–0] = 0.
5	-	MONITOR/MWAIT Parameters. Reports monitor-line size and power hints.	Used in power-management routines.
6	-	Thermal and Power Management. Indicates turbo boost, energy-performance bias, etc.	Features vary by generation.
7	n (0+)	Structured Extended Feature Flags. Lists AVX2, BMI, SMEP, SMAP, SHA, and other extensions.	ECX = 0 = base feature list.
8	-	Reserved (Intel).	Typically returns zeros.
9	-	Direct Cache Access (DCA) Capabilities.	Rarely used outside servers.
10	-	Architectural Performance Monitoring. Gives number and width of performance counters.	Used for profiling/perf events.
11	n (0… until type=0)	Extended Topology Enumeration. Replaces legacy APIC ID method for threads/cores.	Iterate until EAX[4–0] = 0.
12	-	SGX Capability Reporting.	Secure Guard Extensions (if supported).
13	n (0+)	Extended State Enumeration (XSAVE). Reports supported CPU state components and save area size.	Used for AVX and AVX-512.
14	-	Intel Processor Trace.	Reports tracing feature support.
15	-	Time Stamp Counter and Crystal Clock Relationship.	Defines TSC/core crystal frequency ratio.
16	-	Processor Frequency Information.	Base, max, and bus ratio in MHz.
17	n (0+)	System-on-Chip Vendor Attributes.	Vendor ID and capabilities.
18	n (0+)	Platform QoS Monitoring.	Cache and memory bandwidth monitoring.
19	n (0+)	Platform QoS Enforcement.	Cache/memory bandwidth allocation.
20–23	-	Reserved.	May be vendor-specific.
24	-	AMD SEV / Memory Encryption Capabilities.	Only valid on AMD CPUs.
25	-	AMD Performance and Debug Features.	Implementation-specific.
26–29	-	Reserved.	-
30	-	IA32 Architectural Capabilities.	Provides details on RDPID, SGX, etc.
31	-	AVX10 and Architectural Future Extensions.	(Newer CPUs only.)

Extended (High) Leaves

Leaf (EAX)	Sub-Leaf (ECX)	Purpose / Description	Example Outputs or Notes
2147483648	-	Highest Extended Function Supported.	Returns maximum extended leaf.
2147483649	-	Processor Brand String (part 1).	ASCII characters in registers.
2147483650	-	Processor Brand String (part 2).	Concatenate with other parts.
2147483651	-	Processor Brand String (part 3).	Full readable brand string.
2147483652	-	Extended Features (AMD).	Reports long mode (64-bit), NX, etc.
2147483653	-	AMD Brand ID and Feature Extensions.	Reports 3DNow!+, LZCNT, etc.
2147483654	-	AMD Advanced Power Management Info.	Frequency, voltage hints.
2147483655	-	AMD Lightweight Profiling (LWP).	Low-overhead performance monitoring.
2147483656	-	AMD Cache Topology and Address Translation.	Page size and cache info.
2147483657	-	AMD Processor Capacity / Die Identification.	Used for multi-chip packages.
2147483658	-	AMD Encryption and Secure Memory Features.	SME, SEV, SEV-ES flags.
2147483659+	-	Reserved or Vendor-Specific Extensions.	Future-use space.

Notes

All leaf values are shown in decimal form, as used by the cpuid command.
Sub-leaves (ECX) are zero unless iterating over hierarchical data like cache or topology.
The command reads EAX, EBX, ECX, and EDX and prints their raw 32-bit register values in hexadecimal for analysis.
To reconstruct brand strings, concatenate ASCII bytes from the extended leaves (2147483649–2147483651).