I've been working on a simple OS for tinkering and running bare metal apps on vintage PCs.
Since I couldn't quite decide whether to target pure 16-bit, or slightly more capable 32-bit machines, I ended up with two separate versions:
- GentleOS/32 (https://github.com/luke8086/gentleos32) works on i386+, requires 4MB of RAM and VGA display supporting 640x480x16 mode or any 256-color VESA mode.
- GentleOS/16 (https://github.com/luke8086/gentleos) works on 80186+, requires less than 192KB of RAM and a CGA display supporting 320x200x4 mode.
You can find more details in the repos.