GentleOS/16

GentleOS/16 is a hobby OS for vintage 16-bit PCs.

Its minimal requirements are an 8086 CPU with 192KB of RAM, and a CGA display capable of 320x200x4 mode.

It's built specifically for tinkering with old hardware on the bare metal, using plain C. It doesn't have any "practical" use, there's no web browser and no way to run third-party apps.

It's a simplified version of a slightly more advanced OS for 32-bit devices - GentleOS/32, with which it shares most of its design considerations.

Downloads

⚠︎ Warning: GentleOS/16 is written in good faith, but it's experimental and the author takes no responsibility for any lost data or damaged hardware. It is free software, licensed under GPL-2.0, and comes with no warranty. Proceed at your own risk.

gentleos16.img - Bootable disk image that can be written to a 1.44M/720K/360K floppy, HDD or USB flash drive

gentleos16-fd1440.img - 1.44M floppy-sized image for use in emulators

gentleos16-fd720.img - 720K floppy-sized image for use in emulators

GENTLEOS.COM - COM executable that can be started from DOS

Running

For a quick test, install QEMU, fetch the FDD image, and run:

qemu-system-i386 -drive format=raw,if=floppy,file=gentleos16-fd1440.img -m 1

To enable audio support on macOS, also add:

-audiodev coreaudio,id=snd0 -machine pcspk-audiodev=snd0

Gallery

Devices

Photo of GentleOS/16 on Amstrad PPC 512 — Amstrad PPC 512 (NEC V30, 512KB)

Apps

FAQ

Will it run on my PC?

Due to quirkiness of old devices, the only way to know for sure is to check. The lowest hardware configuration tested by the author was NEC V20 CPU and 512KB of RAM. On the high end, the PC must still support BIOS / legacy boot. It won't work on pure-UEFI systems since they don't emulate PS2 keyboard and mouse.

How to debug over serial port?

First you need to recompile it with DEBUG_TO_UART enabled in config.h. Then, my preferred way is to use Serial USB Terminal on Android, through a cheap RS232 to USB-C adapter with PL-2303 chipset, and a mini null-modem F-F adapter. In the app you need to set 9600 baud rate, 8 data bits, no parity, 1 stop bit.