image/svg+xmlPAUSE—Spin Loop HintInstruction Operand EncodingDescriptionImproves the performance of spin-wait loops. When executing a “spin-wait loop,” processors will suffer a severe performance penalty when exiting the loop because it detects a possible memory order violation. The PAUSE instruction provides a hint to the processor that the code sequence is a spin-wait loop. The processor uses this hint to avoid the memory order violation in most situations, which greatly improves processor performance. For this reason, it is recommended that a PAUSE instruction be placed in all spin-wait loops.An additional function of the PAUSE instruction is to reduce the power consumed by a processor while executing a spin loop. A processor can execute a spin-wait loop extremely quickly, causing the processor to consume a lot of power while it waits for the resource it is spinning on to become available. Inserting a pause instruction in a spin-wait loop greatly reduces the processor’s power consumption.This instruction was introduced in the Pentium 4 processors, but is backward compatible with all IA-32 processors. In earlier IA-32 processors, the PAUSE instruction operates like a NOP instruction. The Pentium 4 and Intel Xeon processors implement the PAUSE instruction as a delay. The delay is finite and can be zero for some processors. This instruction does not change the architectural state of the processor (that is, it performs essentially a delaying no-op operation).This instruction’s operation is the same in non-64-bit modes and 64-bit mode.OperationExecute_Next_Instruction(DELAY);Numeric ExceptionsNone.Exceptions (All Operating Modes)#UD If the LOCK prefix is used.OpcodeInstructionOp/ En64-Bit ModeCompat/Leg ModeDescriptionF3 90PAUSEZOValidValid Gives hint to processor that improves performance of spin-wait loops.Op/EnOperand 1Operand 2Operand 3Operand 4ZONANANANA

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