os8088: An AI-Written, Mac-Style GUI OS That Boots a 1981 IBM PC From Floppy

os8088 is a hobby operating system that boots straight from a floppy’s first sector into a graphical desktop modeled on the 1984 Macintosh’s System 1 — overlapping windows, pull-down menus, a serial mouse, drive icons, and a dock of running apps. There’s no DOS and no command line beneath it: a 512-byte boot sector loads a ~40KB kernel that detects the display adapter (VGA, Hercules, or CGA), switches to graphics, and reuses the video card’s built-in 8x8 font. The whole system runs in 256K of RAM on an 8086/8088 and, notably, offers pre-emptive multitasking for up to 12 tasks at 18.2Hz — something neither the period Macintosh nor DR’s GEM ever shipped on this class of hardware. In August 2026 the disk images were written to real floppies and booted on genuine period machines including a 1981 IBM 5150.

The project’s most striking claim is its provenance: the author says the ~112,000 lines of NASM real-mode assembly were written by AI rather than by hand. That reframes it as much as a demonstration of AI-generated low-level systems code as a retro-computing curiosity, since hand-writing a bootable, multitasking GUI kernel in assembly is exactly the kind of dense, unforgiving work usually cited as beyond current code-generation tools.

The design is deliberately minimal and honest about its limits: no memory protection (every program shares one 64K segment with the kernel, which is what makes context switches cheap), no file handles or seeking (the disk API moves whole files at a time), and no networking. The author frames os8088 as an argument with history — a rebuild of the Mac-style PC desktop that GEM 1.0 briefly delivered in 1985 before Apple’s lawsuit forced its overlapping windows and icons off the PC. A browser demo and downloadable images for period hardware, 86Box, and QEMU are available.