Ever since the earliest days of computing, scientists and engineers have focused on building machines that were smaller, faster, and less expensive than the previous generation. Now, one British man has taken it upon himself to reverse that trend. James Newman, of Cambridge, recently unveiled his completed “Megaprocessor” — a fully functional CPU built to human scale, with LEDs that light up at every stage of the computational process to show how data moves through a circuit.
The Megaprocessor is a 16-bit design with four general-purpose registers, a program counter, a processor status register, and a stack pointer. It has 256 bytes of memory and a 500W power supply (most of the latter is dedicated to the LEDs). The memory block contains 27,000 transistors. The CPU’s transistor count comes out to 15,300, but much of this is also devoted to the LEDs. Subtract those from the equation, and the total CPU transistor count seems to be about 6,800. That’s roughly 2x as many as the original 6502 microprocessor, though the 6502 was a bit smaller. Computation is handled via a 16-bit ALU and 16-bit adder — there’s no word on whether or not Newman intends to offer a separate floating point unit, though the installation requirements for such hardware would likely be formidable.
If you’re wondering how a person ends up building a Megaprocessor in the first place, Newman notes that his project started as an attempt to understand the operation of a transistor, before noting “I didn’t plan on ending up here. I started by wanting to learn about transistors. Things got out of hand.” When you start off wanting to learn about transistors, and instead build a giant implementation of one that fills most of a house, that seems an apt way to describe the situation.
What drove Newman was wanting to be able to show, viscerally, how data moves across a CPU as it executes a program. “Computers are quite opaque,” Newman said. “Looking at them, it’s impossible to see how they work. What I would like to do is get inside and see what’s going on. Trouble is we can’t shrink down small enough to walk inside a silicon chip. But we can go the other way; we can build the thing big enough that we can walk inside it. Not only that we can also put LEDs on everything so we can actually SEE the data moving and the logic happening. It’s going to be great.”
The video above shows the Megaprocessor in action, and it’s hard not to be impressed by the idea. Anyone can study a logic diagram, but that’s not the same thing as actually seeing components in person and being able to watch them function in real time. It’s easy to forget, given that we live in an era in which transistors are packed by the billions into a few hundred millimeters, but there was a time when transistors and integrated circuits were laid out by hand. A CPU’s bus used to be something you could literally see, and not simply as a collection of copper traces on a motherboard.
While few would want to return to the limited computer power of this earlier era, the Megaprocessor is an impressive piece of work. Hopefully some enterprising programmer will get to work figuring out how to execute cryptocurrency hashing on it — we’d love to see the Megaprocessor take on the IBM 1401 mainframe in an epic bitcoin battle.