ISIS-II Simulator

ISIS-II was an operating system developed by Intel in the mid-70s for their MDS (Microprocessor Development System). The MDS was an 8080-based system that ran on 8-inch floppies. It included an assembler, a compiler for PL/M (a high-level programming language streamlined for microprocessors), a linker, and associated tools.

There’s no reason why this ancient software would be useful any more. The 8080 processor, though very popular in the 70s, quickly gave way to the 16-bit 8086, which evolved into the CPUs that power most PCs nowadays. It’s likely that very few embedded systems in the world today use the 8080, or its very similar competitor, the Zilog Z80.

But we can still see the 8080 influence even in these modern processors, for good or ill. And I like the idea of keeping around old software just to remind myself of the good old days, when chips and systems were so simple that one person could easily comprehend them in their entirety.

So I’ve written an simulator for ISIS-II, which obviously includes an 8080 simulator. Clone the git repository using this command:

git clone

It currently builds and runs on either 32-bit or 64-bit Linux. It was originally written back in the 80s for DOS, but I haven’t done the necessary work to update it to work on Win32.

The package includes free copies of Intel’s linker, assembler, and PL/M compiler that I obtained from Intel’s web site. After you unpack the tar file, run make to build the simulator. Then run make test to make sure that everything’s working; this will compile a simple PL/M program and run it on the simulator. You must be using bash as your shell for this to work.