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by blattimwind 2805 days ago
It's only a superficial analogy. Micro-ops were RISC-like in the sense that they used to do one / few things. But their implementation is unlike RISC, micro-ops typically being very large (100+ bits wide) and not even necessarily of fixed length; you may imagine a specific bit in a micro-op more or less directly controlling a certain control line somewhere in an execution unit. Conversely micro-ops also can do a whole bunch of things at the same time.
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You have to distinguish between micro instructions in the meaning of "line in microcode store" which for the horizontally microcoded CPUs contain bits that more or less directly map onto datapath control signals and micro operations in the superscalar x86 sense, which typically are more or less reformulation of x86 instructions into something that is both more easy to execute in parallel (which involves breaking instructions into their constituent suboperations, which are RISC-like in the load-store sense, not in the other RISC characteristics) and maps better to the actual execution units (which may involve combining instructions).