Calling CPUID in C and C++ĬPUID can be used in C and C++ as well. The above code sets the value of 0 to EAX as input and then, calls the instruction CPUID. Therefore, before calling CPUID, the correct input value should be set in EAX and ECX.įollowing is a valid assembly code calling CPUID for leaf value 0: MOV EAX, 00h In assembly programming language, CPUID can be used directly as it will use the value stored in EAX and ECX. The opcode of CPUID is 0Fh, A2h (= A20Fh). To know for which input, what information is provided, you need to consult the CPUID Specification document for the Processor you are using.

ECX: known as sub-leaf Optional input Needed only for specific functions.ĬPUID instructions provide 4 outputs stored in 4 different registers:.Input determine the information returned by the CPUID instruction. Extended: returns information about extended processorĬPUID instructions deal with 4 registers: EAX, EBX, ECX, EDX.Basic: returns basic information about processor.Let us get started with CPUID (CPU Identification). Today, CPUID (CPU Identification) is supported in many CPU processors including Intel and AMD. It is supported in x86 architectures and was introduced in 1993 by Intel. CPUID (CPU Identification) is a set of instructions that is used to fetch information about the Processor such as Processor Topology, Cache Size and much more.

Intel cpu identifier