Really, Really Retro Computer On An FPGA

[Daniel Bailey] built himself a scaled-down clone of a very early computer in an FPGA. Specifically, he wrote some VHDL code to describe the machine in question, a scaled-down clone of the Manchester Small-Scale Experimental Machine with an 8-bit processor and a whopping 8 bytes of RAM, all of which are displayed on an LED screen. Too cool.

That he can get it to do anything at all with such constraints amazes us. Watch him program it and put it through its paces in the video below the break.

The coolest thing about the original “Manchester Baby” is that it retains memory in a Williams tube, which is essentially a CRT with an electrical pickup plate covering up the screen. You know how you get a static charge on the face of an old CRT where the electron beam hit? Well, it turns out that you can read this electric field for a while, and use it as a short-term memory element.

The builders of the SSEM included a second CRT screen so that you could visualize the entire 32×32 bits of memory on a screen, like you would. Naturally, [Daniel] had to replicate this feature on his Manchester Baby clone, but with an 8×8 LED matrix. Now we want one of those for our laptop.

The VHDL is up on Github, as is a Javascript simulator of the machine. And if you’re interested, there’s an active retro-computing Google+ group where this and similar projects are bantied about. And check out some of the earliest computer music, made on a descendant of the Manchester Baby.

Thanks [Ed] for the tip.

10 thoughts on “Really, Really Retro Computer On An FPGA

  1. This reminds me of my first computer, the ‘Mini-Scamp’ from the local magazine and sold by Dick Smith here in Australia. Based on the SC/MP it had toggle switches on the front. Unlike this one it had 8 address bits. Nearly 40 years later and I have not got sick of this stuff yet. :)

  2. I think My fingers still hurt from entering “programs” via the 16 switches “keyboard” on the UYC-20. Programs were literally the ones and zeroes of the assembly code.

  3. actually that’s the way wozniak and steve put in their first programs. and they didn’t have a non volatile memory too… so after power loss they had to do the fun part again.

  4. I want to see someone take the design of the paperclip computer, build it with manufactured switches and other components, and automate the functions one must perform manually with the original design. Sticking to mechanical systems, that would require solenoids to actuate the switches, or relays.

    Could get complicated rather quickly.

    When I first looked through that old document, I noted the hand made rotary Binary Coded Decimal switches but I missed that the “memory” made of twisted paperclips was actually just a bunch of manually actuated switches, not a crude form of hand crafted magnetic core. *sigh* That would have been cool. Per the original design, “loading” a program from the coffee can drum is a tedious process of reading light bulbs activated by the bar and insulated spots on the can then manually closing bit switches.

    It does illustrate all the base functions of any binary computer from the earliest to the most current – by brute force method of making the operator personally actuate every single switch and move of every bit. A very good reason so few of these were ever built. Why not just do the math with pencil and paper?

    Putting the paperclip computer into an FPGA would make it easy to automate it all, but you’d lose the cool mechanicals and blinken lichten.

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