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by pmalynin 4024 days ago
Not exactly, most instructions are not "microcoded" for performance reasons. But there is a class of instructions that is.
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Intel CPUs translate x86 to some internal RISC-like "uops" before doing optimizations and execution. This is a widely documented fact (though Intel doesn't really talk publicly about it as far as I know): see for example ยง2.1 in http://www.agner.org/optimize/microarchitecture.pdf
For a (hopefully!) more accessible introduction to the crazy world of what really happens inside the x86, I did a talk at GOTO: http://youtu.be/hgcNM-6wr34 - it's a really fascinating subject!
For marketing reasons, Intel made quite a big commotion over the fact that its Pentium was "RISC-like" when it was first released, but in reality what it meant was using a decoder that could emit multiple uops in parallel instead of sequentially like it was in the 486.

Even CPUs considered RISC today, like ARMs, need to decode instructions into one or more wider uops for efficient execution.