These are a few sites I've come across in my travels. The quality level
varies a lot. In most cases,
the descriptions are provided from the webmaster from the specific site.
BOS is a 32 Bit OS written in assembler in 2001. No recent updates, but still available.
Assembler-only OS for 32-bit x86 processors.
of Operating Systems
A Review of Operating Systems, stressing on free, original, actively
Rocky Coast Free Board
Free Software tools for programmers, along with
all the links to other OS and programming Web sites.
- A Teachable Operating System
Topsy is a small (~20k machine code) multi-threaded micro kernel. It
is written in ANSI C and protects kernel threads from user programs.
It supports memory management, thread/process control and an IO and
driver subsystem. Communication and synchronization is implemented with
messages. Topsy runs on MIPS R3000 and i386 based machines. A simulator
written in Java is available.