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Notes on the Pentium's microcode circuitry

Accepted submission by owl at 2025-03-31 18:43:00
Hardware
https://www.righto.com/2025/03/pentium-microcde-rom-circuitry.html [righto.com]

Most people think of machine instructions as the fundamental steps that a computer performs. However, many processors have another layer of software underneath: microcode. With microcode, instead of building the processor's control circuitry from complex logic gates, the control logic is implemented with code known as microcode, stored in the microcode ROM. To execute a machine instruction, the computer internally executes several simpler micro-instructions, specified by the microcode. In this post, I examine the microcode ROM in the original Pentium, looking at the low-level circuitry.


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