Gloriouscow

Ken Shirriff's post reverse-engineers the 8087 FXCH microcode, revealing detailed micro-instruction flow, ROM size, and die architecture.

Open-source z386 reconstructs the 80386 around original microcode in FPGA, enabling real DOS software and Doom, with a compact 16KB VIPT L1 cache and a 37-bit microcode word design, benchmarked against ao486.

Disassembles the 80386 microcode, revealing a very large microcode ROM (94,720 bits) and 215 entry points with full microcode coverage, plus a potential IO-port permission bug and open-source references.