Content deleted Content added
Guy Harris (talk | contribs) →Examples: The 486, according to https://ieeexplore.ieee.org/document/63682, doesn't execute simple instructions directly in hardware, although those instructions decode to only one microinstruction. |
Guy Harris (talk | contribs) →Micro-operations: That begins with the P6 (which dates back almost 20 years, so "modern" isn't all that modern). |
||
Line 284:
==Micro-operations==
Modern CISC implementations, such as the [[x86]] family starting with the [[P6 microarchitecture]], 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]].
| |||