RSX180 is an Operating System for the Zilog Z180 CPU that is similar in look and feel to the old DEC's RSX-11M.

Features:

• Multi-tasking.
• Multi-user.
• Multi-terminal.
• Priority-based micro-kernel with round-robin scheduling of tasks of the same priority.
• QIO mechanism.
• AST support.
• Event Flags.
• Send-Receive inter-task communication mechanism.
• Kernel functionality extended by privileged tasks.
• Task Directory for fast task activation.
• Tasks can be fixed in memory for even faster activation.
• Device drivers.
• Dynamic allocation of system resources.
• Fork processes.
• Clock queue and time-scheduled task execution.
• Privileged and non-privileged users.
• 2-level filesystem structure.
• Indirect Command Processor.

More details here.

P112 CPU board (Z182) with:

• Kernel: Dallas DS1202/DS1302 (RTC and NVRAM)
• Terminal driver: two serial ports (Z182 and FDC37C655)
• Floppy disk driver (FDC37C655)
• Hard disk driver (GIDE)
• Parallel (printer) port (FDC37C655)

Follow the instructions listed in the Docs/Compiling.txt file.

Please note that this still is a work in progress. The kernel is rather complete and stable, the system can be booted and used, but there are many unfinished details, some basic utilities are still missing features and bugs are very likely hiding somewhere in the code.