ARM processors are literally powering the world. They are the brains behind a multitude of machines, from programmable espresso machines, to large-format printers, and even robotic arms in factories. Originally designed by Acorn Computers in the UK, the ARM IP was spun off before the founding company imploded, and today the ARM Foundation designs chips for companies that can be licensed and produced, and even tailored, for anyone with the money and fabrication space for them. They’ve been doing this for 25 years and are, quite literally, a more influential chip-designer than Intel. But the very first ARM processor, the ARM1, was almost lost to time, and was a prototype design that was never intended for public use. Thanks to a number of people working with ARM, the original blueprints for the chip have been recovered, and the Visual6502 blog has even published a simulator for the chip that can be run in your browser. Interested in programming for ARM? Hit the jump for more!

What’s fascinating about ARM CPUs is that modern designs still have their roots in the ARM1 architecture, and most programs developed for 32-bit ARM processors in the late 1980s can still be run on modern chips today, with a little tweaking for newer instruction sets. ARM processors are RISC-based, which means that they lack the dozens of extra instruction sets found on other processors, which makes them simpler to design and produce, and more efficient for the kind of work they’ll be doing. There are 64-bit ARM designs, but they’re not as prevalent as the 32-bit versions.

The simulator for the ARM1 processor, which you can find in the links below, was compiled through recovering the blueprints for the architecture, as well as other important documents relating to the chip’s design. The Visual6502 team worked with ARM engineers John Biggs, Lee Smith and founder Dave Howard to recover plans that also detailed the workings of the chip at a transistor level, as well as documents related to how the CPU worked with system memory. The simulator is written in Javascript, and is designed to be an exact replica of the real thing, living on in software for archival purposes.

You can either run the simulator through a set of code and see in real-time how the logic gates work as the “chip” crunches through them, or head on into the advanced mode, where you can submit your own code and see the chip execute it. Not only is this simulator accurate, it’s also a great way to test out code you’ve written for ARM chips that might be similar to the ARM2 or ARM3, which are similar to the ARM1 with a few advanced features added.

Even if you’re not interested in writing code for ARM CPUs, head on over to the link anyway and see for yourself how a CPU works in real-time. It’s fascinating to watch, and makes me wish I had studied computer science and electrical engineering when I was in college. Make sure you’re using a modern browser, and have a dual-core CPU running at 2.0GHz, and 1GB of RAM to have this simulator run properly.

Source: The Register

Run the simulator: Normal Mode / Advanced Mode