80386 Microcode Disassembled
The disassembly of the 80386 microcode has been achieved after significant effort and collaboration. Initially considered a daunting task due to its complexity and size, the project progressed through image processing and AI techniques. Ultimately, the team successfully associated 386 instructions with corresponding microcode, revealing the architecture's advancements over the 8086.
- ▪The 80386 microcode consists of 94720 bits, significantly larger than the 8086's 10752 bits.
- ▪Collaboration among enthusiasts led to the extraction and disassembly of the microcode from high-resolution images of the 80386 die.
- ▪The 80386 features 215 entry points in its microcode, a notable increase from the 60 found in the 8086.
Opening excerpt (first ~120 words) tap to expand
After 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) so (even with bitract or similar) it would be extremely tedious to transcode and check. The other reason is that I wouldn't know where to start with it - at least with the 8086 there was a patent which gave the general outline and some chunks of code which I could search for. 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.
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