Intel Microcode - Wikipedia

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2021-06-08 02:00:08

Intel microcode is microcode that runs inside x86 processors made by Intel. Since the P6 microarchitecture introduced in the mid-1990s, the microcode programs can be patched by the operating system or BIOS firmware to workaround bugs found in the CPU after release.[1] Intel had originally designed microcode updates for processor debugging under its design for testing (DFT) initiative.[2]

Following the Pentium FDIV bug the patchable microcode function took on a wider purpose to allow in-field updating without needing to do a product recall.[1]

In the P6 and later microarchitectures, x86 instructions are internally converted into simpler RISC-style micro-operations that are specific to a particular processor and stepping level.[1]

On the Intel 80486 and AMD Am486 there are approximately 250 lines of microcode, totalling 12,032 bits stored in the microcode ROM.[3]

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