GLaBIOS
A modern, scratch-built, open-source alternative BIOS for vintage PC, XT, 8088 Clone or Turbo PCs.
Copyright © 2022-2026, 640KB and contributors.
Version 0.8 (beta):
Download ROMs
Version 0.4 (stable):
Download ROMs
Source Code
Features
- A complete 100% PC Compatible BIOS for retro/vintage PC, XT, 8088 Clone, Turbo, Homebrew PCs and more!
- Colorful POST screen with useful information such as CPU, FPU, port addresses, floppy drives and hard disk geometry.
- FAST! Performance-optmized CGA/MDA text and graphics routines.
- 5150 Cassette tape support.
- NEC V20 enhanced instruction set support.
- Multiple levels of “CGA snow” removal (configurable at build-time).
- Accurate PIT-based I/O timing for floppy disk for faster seek and read times.
- Customizable POST test screen colors themes.
- Fits in an 8K ROM to drop in to any original PC or clone.
- Complete Extended Keyboard support (new in version 0.8!)
Companion ROMs
Companion ROMs are PC Option ROMs that add additional features and support to any standard BIOS (not just GLaBIOS).
- GLaDISK - High Density Floppy drive support.
- GLaTICK - ROM based support for ISA Real Time Clocks providing
INT 1Ah services elimiating the need for DOS programs/drivers.
FAQ
Why another 8088 PC BIOS in 2022 2023 2024 2025 2026?
There are other excellent BIOS projects out there each with it’s own design goals and use cases. The goals for GLaBIOS are:
- A collborative learning effort among the Retro Community
- A fully open-source PC BIOS, built and improved by the community, free of outside proprietary or copyrighted code
- Feature-complete with full support for original vintage hardware as well as new projects
Where did the name originate?
If you aren’t familiar with the reference, ask a gamer.
How can I try it?
Click here for how to make the BIOS ROMs.
OR try it LIVE!
Building GLaBIOS
How to Build Wiki page
More questions?
Check out the Wiki!
Screenshots
VGA with 8087 FPU and GLaTICK:
EGA with V20:
CGA with 736K memory:
Bad RAM detected! Use standard address and bit indicator to locate failed IC:
5150 with cassette:
Compatibility
1-2-3 ver 1A
Flight Simulator 1.0
Please send bug reports, feedback, questions or thoughts to [email protected], submit an Issue or Discord.
References and Credits:
Further Credits to:
- The Code Golf (CGCC) community on Stack Exchange for helping me become a better ASM programmer.
- @dbalsom (aka gloriouscow) for moral support and the incredible MartyPC emulator software.
- @Raffzahn, Contributor, Advisor and Meckerhut.
- @MadMaxx12345, @Makefile, @punishedbunny, @PickledDog, @sqpat and many others for testing, bug finding and feature suggestions.
- Hampa Hug for the excellent PCE software that helped make development and debugging much easier.
- Dave Nault, my partner in crime for 2 semesters of college assembly language programming classes back in the day. Wherever you are buddy, hope you’re doing well!
License
- GNU General Public License v3.0. See LICENSE.
Disclaimer
This project is built upon the collective knowledge of the community by and for the benefit of the community. Unless stated otherwise, cited public sources are considered as “public domain” or “fair use” of the copyrighted material as provided for in section 107 of the US Copyright Law. If your copyrighted material appears in this project or on this web site and you disagree with our assessment that it constitutes “fair use,” contact us.
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