GentleOS/32

* Project handcrafted by a human

GentleOS/32 is a nostalgic hobby OS for vintage 32-bit PCs with a retro-style GUI, a handful of built-in apps, and a selection of classic games.

Its minimal requirements are an i386 CPU with 640KB of RAM, a mouse, and a VGA display supporting 640x480x16 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 has a pure 16-bit spin-off called GentleOS/16, which targets even older PCs.

Try in your browser

Open this page in a desktop browser to run an online PC emulator

Click here to launch GentleOS/32 in an online PC emulator.

Design

Unlike many other hobby osdev projects, GentleOS doesn't attempt to mimic general-purpose systems. It's designed more like microcontroller firmware - entirely monolithic and compiled to a single binary.

It's written in a simple subset of plain C with small bits of assembly. The source code is meant to be straightforward and easy to understand.

It only supports standard PC devices: VGA/SVGA, keyboard, PS2/serial mouse, PC speaker.

By design it doesn't support virtual memory, userspace, preemptive multitasking, persistent storage or networking. The only future development plans are refactoring, bugfixes, optimizations, and adding more apps.

Gallery

Photo of GentleOS/32 on ThinkPad 380Z — IBM ThinkPad 380Z (Pentium 2)

Photo of GentleOS/32 on Toshiba T1800 — Toshiba T1800 (Intel 386SX/20)

Photo of GentleOS/32 on Toshiba Libretto 20 — Toshiba Libretto 20 (AMD 486 DX4)

Downloads

⚠︎ Warning: GentleOS/32 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.

gentleos32-disk.img - Bootable disk image that can be written to a 1.44M/720K/360K floppy, HDD or USB flash drive.

gentleos32-grub.img - Alternative disk image with GRUB 2. It requires 4MB of RAM.

gentleos.bin - Kernel file that can be booted with either GRUB 2, GRUB Legacy or GRUB4DOS.

Q&A

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 386SX/16MHz CPU with 1MB 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.

Does it support serial mouse?

Yes, you can turn it on in the bootloader menu, or later by pressing Ctrl+Shift+S.

How to debug over serial port?

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. On boot you need to select debug mode from the menu, or if using GRUB, add serial=debug to the kernel command line.

How to set a wallpaper?

You can find the instruction in the README.

Are the photos real? The screen on my device doesn't look that good.

They're real, taken with an iPhone 16, and lit using a softbox. Only minor adjustments were done in GIMP - trimming, white balance, exposure, and contrast.

How to contribute?

I'm making this project for fun in my spare time and sharing it as-is. I don't really accept pull requests because I already have plenty of them to review at work. However, if you do anything interesting with it, please drop me an email! Make sure to mention if you're happy with your changes being included in my branch or on the website.