Disassembling the 80386 Microcode: A Deep Dive into Intel's Processor Architecture
By
nand2mario
A baker's-dozen of insight crammed into one ring.
Summary
A technical blog post detailing the author's process of disassembling and analyzing the microcode ROM of the Intel 80386 microprocessor. The author describes receiving a high-resolution image of the microcode ROM from Ken Shirriff, the challenges of working with a 94,720-bit ROM (compared to the 8086's 10,752 bits), and the methods used to decode and understand the microcode. The post covers the architecture of the 80386's microcode, including the microinstruction format, control signals, and how the processor executes complex instructions through microcode sequencing.
Key quotes
· 3 pulledAfter I posted 8086 microcode disassembled, Ken Shirriff sent me a high-resolution image of the microcode ROM from the 80386.
I didn't expect I would ever do anything with it for a couple of reasons: one is that it's absolutely huge (94720 bits) compared to the 8086 one (10752 bits)
The 80386 was a complete black box. I knew what it did and had a rough idea of how it might work but that turning that into something that I could search for in a big blob of binary seemed like an insurmountable challenge.
You might also wanna read
Reverse-engineering the Intel 8087: A look at microcode and register exchange
A detailed technical deep-dive into the Intel 8087 floating-point co-processor's microcode, specifically examining the register exchange ope
righto.com·1d ago
How Anthropic contains Claude's expanding access across its products
Anthropic describes how it has evolved its approach to granting Claude, its AI assistant, increasingly broad access to internal systems over
anthropic.com·3h ago
Testing Cursor's Jira integration: How ticket quality affects AI agent performance
Cursor launched a Jira integration that lets developers assign tickets directly to an AI agent, eliminating context switching. The author te
bit.ly·3h ago
Netflix engineer's open-source tool cuts AI token usage by up to 90%
Netflix senior engineer Tejas Chopra created software called "Project Headroom" that prunes redundant tokens from AI agent instructions befo
theregister.com·3h ago
Anthropic Releases Free Security Plugin for Claude Code Terminal to Detect Vulnerabilities
Anthropic has released a free security-guidance plugin for its Claude Code terminal tool that autonomously reviews code edits, model outputs
cybersecuritynews.com·4h ago
Researcher's "ADHD" tool for Claude Code claims 2x improvement; experts call for more evidence
Solo researcher Udit Akhouri released a third-party Agent SDK tool called "ADHD" for Claude Code on Reddit, claiming it helps coding agents
bit.ly·4h ago