Micro-operation

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Micro-operations, also known as a micro-ops or μops, are simple, RISC-like microprocessor instructions used by some CISC processors to implement more complex instructions.

A typical CISC processor provides a large, complex set of instructions, in which each instruction executes several low-level operations. RISC processors have demonstrated that a smaller, simpler set of instructions can allow an improvement in performance. As a result, some modern CISC processors now utilize a two-level approach. They still provide the complex "macroinstructions" found in previous iterations, but implement them as a sequence of simpler instructions, or micro-operations, that resemble typical RISC instructions. When the processor receives a macroinstruction, it decodes the instruction into a series of these micro-operations.

To further improve performance, some processors cache the decoded micro-operations, so that if the same macroinstruction is executed again, the processor can directly access the decoded micro-operations from cache, instead of decoding the macroinstruction again. The Execution Trace Cache found in Intel's NetBurst Microarchitecture is example of this. The size of this cache is often stated in terms of how many thousands of micro-operations it can store, or kμops.