Intel® Extended Memory 64 Technology Software Developer's Guide

CPUID—CPU IdentificationOpcode Instruction 64-Bit Mode Compat/Leg DescriptionMode0F A2 CPUID Valid Valid Returns processor identification and featureinformation to the EAX, EBX, ECX, and EDXregisters, according to the input value enteredinitially in the EAX registerDescriptionWhen the input value in the EAX register is 0, the processor returns the highest value the CPUID instruction recognizesin the EAX register for returning basic CPUID information (see Table 2-5). A vendor identification string is returnedin the EBX, EDX, and ECX registers. For Intel ® processors, the vendor identification string is “GenuineIntel” asfollows:EBX ← 756e6547h (* "Genu", with G in the low nibble of BL *)EDX ← 49656e69h (* "ineI", with i in the low nibble of DL *)ECX ← 6c65746eh (* "ntel", with n in the low nibble of CL *)Initial EAXValue0H1H2H3HEAXEBXECXEDXEAXEBXECXEDXEAXEBXECXEDXEAXEBXECXEDXTable 2-5 CPUID Function LeafInformation Provided about the ProcessorMaximum Input Value for Basic CPUID Information (see Table 2-6).“Genu”“ntel”“ineI”Version Information (Type, Family, Model, and Stepping ID)Bits 7-0: Brand IndexBits 15-8: CLFLUSH line size. (Value returned ∗ 8 = cache line size)Bits 23-16: # of logical processors per physical packageBits 31-24: Processor’s initial local APIC IDFeature Information (see Figure 2-8)Feature Information (see Figure 2-8)Cache and TLB InformationCache and TLB InformationCache and TLB InformationCache and TLB InformationReservedReservedReservedReservedVol. 1 2-89