z386: An Open-Source 80386 Built Around Original Microcode
The z386 project has successfully developed an open-source 80386 CPU based on original Intel microcode. This FPGA-based CPU can run real software, including DOS 6 and DOS 7, and is designed to be both educational and functional. While it performs comparably to a fast cached 386-class machine, it incorporates modern FPGA techniques to enhance its capabilities.
- ▪The z386 project is the fifth installment in the 80386 series and aims to recreate the original Intel microarchitecture.
- ▪It can run protected-mode programs and classic games like Doom and Cannon Fodder.
- ▪The design incorporates both traditional 386 structures and FPGA-friendly optimizations.
Opening excerpt (first ~120 words) tap to expand
z386: An Open-Source 80386 Built Around Original Microcode May 23, 2026 by nand2mario This is the fifth installment of the 80386 series. The FPGA CPU is now far enough along to run real software, and this post is about how it works. z386 is a 386-class CPU built around the original Intel microcode, in the same spirit as z8086. The core is not an instruction-by-instruction emulator in RTL. The goal is to recreate enough of the original machine that the recovered 386 control ROM can drive it. Today z386 boots DOS 6 and DOS 7, runs protected-mode programs like DOS/4GW and DOS/32A, and plays games like Doom and Cannon Fodder.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Github.
