![]() The exception to this rule is the input values that return extended function information. For example, if an input value of 5 is entered in EAX for a Pentium 4 processor, the information for an input value of 2 is returned. If a higher value entered than is valid for a particular processor, the information for the highest useful basic information value is returned. Two types of information are returned: basic and extended function information. The second table shows the maximum CPUID input value recognized for each family of IA- 32 processors on which CPUID is implemented. ![]() The following shows information returned, depending on the initial value loaded into the EAX register. 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. The instruction's output is dependent on the contents of the EAX register upon execution. If a software procedure can set and clear this flag, the processor executing the procedure supports the CPUID instruction.ĬPUID returns processor identification and feature information in the EAX, EBX, ECX, and EDX registers. The ID flag (bit 21) in the EFLAGS register indicates support for the CPUID instruction. ![]() Returns processor identification and feature information to the EAX, EBX, ECX, and EDX registers, according to the input value entered initially in the EAX register. X86 Instruction Set Reference CPUID CPU Identification Opcode
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