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In the x86 architecture, the CPUID instruction (identified by a CPUID opcode) is a processor supplementary instruction (its name derived from CPU Identification) allowing software to discover details of the processor.
Special purpose instructions also often lack explicit operands; for example, CPUID in the x86 architecture writes values into four implicit destination registers. This distinction between explicit and implicit operands is important in code generators, especially in the register allocation and live range tracking parts.
The update contains information about which processors it is designed for, so that this can be checked against the result of the CPUID instruction. [1] The structure is a 48-byte header, followed by 2,000 bytes intended to be read directly by the processor to be updated: [ 1 ]
Takes as input a CPUID leaf index in EAX and, depending on leaf, a sub-index in ECX. Result is returned in EAX,EBX,ECX,EDX. [d] Instruction is serializing, and causes a mandatory #VMEXIT under virtualization. Support for CPUID can be checked by toggling bit 21 of EFLAGS (EFLAGS.ID) – if this bit can be toggled, CPUID is present. Usually 3 [e]
The CPUID instruction can be used on both AMD and Intel CPUs to check whether the RDRAND instruction is supported. If it is, bit 30 of the ECX register is set after calling CPUID standard function 01H. [10] AMD processors are checked for the feature using the same test. [11] RDSEED availability can be checked on Intel CPUs in a similar manner.
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The types of operations may include arithmetic, data copying, logical operations, and program control, as well as special instructions (e.g., CPUID). [10] In addition to the opcode, many instructions also specify the data (known as operands) the operation will act upon, although some instructions may have implicit operands or none at all. [10]
The clipped video does not show that the hand the VP tried to shake was holding on to a cane,” Federalist editor-in-chief Mollie Hemingway wrote on X. Sen. Deb Fischer was sworn into her third ...