One Page Computing Challenge

Roll your own challenge: computing in 66 lines of printout - homebrew CPU, or emulator, or both! Or anything really.

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Here's a challenge for everyone interested in CPU design - design something small. In fact, so small you can fit it on one page.

To keep it fun, make up your own idea of what that means - one page of spec, or one page of schematic, or one page of HDL, or a one-page emulator in the language of your choice. If you can write a one-page monitor, or any application in one page, that's interesting too!

There's a thread for discussion and contributions over on the AnyCPU forum: see

And if you want to define one page as a huge page with tiny font, go ahead! Personally I'm more interested in the 66-line fanfold paper, which is I think 132 characters across. I hope not to code-golf, so the code is remains readable and self-explanatory. I just might allow myself to print at 8 lines per inch, and get 88 lines to the page.

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Julian wrote 06/14/2018 at 02:36 point

My entry: -- a 6-bit pipelined CPU with schematic that fits on a single page.

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Ed S wrote 07/10/2018 at 18:01 point

A 6-bit Harvard homebrew CPU - excellent! Thanks for posting to the #One Page Computing Challenge 

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Jade wrote 04/19/2018 at 03:36 point

Here's what I made today:

Here's an image, with the extra register and little LEDs to tell you what data is being sent where.  (the register (OUTPUT_REG) is a fill-in for a co-processor, since the way that it communicate is through a shared register anyway)

someone please tell me how to embed images properly

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Ed S wrote 07/13/2017 at 20:05 point

See our #OPC-5 - a CPU for FPGA, in one page which is still evolving but has been seen to compute hundreds of digits of Pi. It's a 16-bit wide, word-addressed machine, with 16 registers.

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Ed S wrote 06/25/2017 at 14:59 point

What would be a good a demonstration that the one-page creation is indeed a computer? For me, controlling some hardware according to a program is ample demonstration, and for a more conventional machine, some kind of numeric processing, for example something like any one of these:

- print out the first N squares [1]

- the first N Fibonacci numbers

- the first N primes

- the first N square roots

- the first N digits of e

- the first N digits of pi

- Mastermind / cows and bulls game

- Higher/Lower guess a number game

- Lunar Lander game (not real time, of course! Turn-based.)

[1] Historically interesting: EDSAC ran a squares and differences program written by Wilkes. It had multiplication, so squaring was easy, but printing numbers in decimal always takes effort.

Running any kind of HLL interpreter would support any of those programs, but they could equally well be written in assembler. I'd be surprised to see a reasonable interpreter in one page.

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Ed S wrote 06/24/2017 at 15:16 point

Our #OPC-1 CPU for CPLD is a one-page cpu.

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agp.cooper wrote 06/17/2017 at 06:48 point

Okay, here is mine (but it is a rather long page): 

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Ed S wrote 06/17/2017 at 06:52 point

Ooh, a TTL machine - transport triggered - 8 bit - what's not to love?

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agp.cooper wrote 06/17/2017 at 07:32 point

Built in Front Panel, built and working.


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agp.cooper wrote 06/17/2017 at 07:39 point

Here is the monitor program and the LED light chaser program:

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Ed S wrote 06/17/2017 at 07:52 point

Maybe you can join in over on the AnyCPU forum: see


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Ed S wrote 05/28/2017 at 21:04 point

As you wish - the nice thing about this challenge is that you make your own constraints.

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Yann Guidon / YGDES wrote 05/28/2017 at 20:50 point

entries are in a PDF file with a single page ? :-)

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Ed S wrote 06/03/2017 at 06:41 point

(Actually that printout is from a web page - CSS can do green bar paper! With a background image for the holes. See

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