Microcode: Difference between revisions

Revision as of 12:31, 26 February 2025

Revision as of 01:21, 8 March 2025

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==Micro-operations==

Modern CISC implementations, such as the [[x86]] family starting with the [[NexGen]] Nx586, Intel [[Pentium Pro]], and [[AMD K5]]., decode instructions into dynamically buffered [[micro-operation]]s with an instruction encoding similar to RISC or traditional microcode. A hardwired instruction decode unit directly emits microoperations for common x86 instructions, but falls back to a more traditional microcode ROM containing microoperations for more complex or rarely used instructions.<ref name=FogMicro/>

For example, an x86 might look up microoperations from microcode to handle complex multistep operations such as loop or string instructions, [[floating-point unit]] [[transcendental function]]s or unusual values such as [[denormal number]]s, and special-purpose instructions such as [[CPUID]].