Electron tube New Automatic Computer


Ena.Computer, a tube computer for the 21st century.

Built just for the fun of doing it, with a blind faith

due to my total misjudgement of the project's complexity


The Ena.Computer is a modern, general purpose, 8 bit computer, with the usual 12 bit address and data buses plus the unusual current demand of 200 Amps.

A computer that is both competent and dangerous.

After switch on you have to wait a while for the last electron tube to warm up. If you look from the side you see a few start to show a red glow. After about a minute the Ena.Computer has the pleasant homely aroma of 550 double electron tubes, quietly burning off their dust.

When all the tubes are glowing, I check the fire extinguisher is full, and run the code.

Ena.Computer first ran on 28th May 2021 on our dining room table, chairs and surrounding floor space.

The Final Configuration, with all its bells and whistles, is now firmly nailed to the study wall, and is almost safe to touch.

It has been a ridiculous amount of soldering and a fantastic amount of fun.




The Why, The When, and The Where

After visiting Bletchley Park, it occurred to me that several tube computers had been rebuilt, and now run in museums, but that no new design of a tube computer had been constructed in over 50 years. The thought of building one seemed ridiculous, but I wondered if a modern design could overcome the issues of size, power and the very real danger of high voltages.

When I retired I looked at the problem again and realised it could be an interesting and enjoyable endeavour.
I spent almost a year designing and building the Ena.Computer.
Please note that high voltages are very dangerous and shouting bang when a friend has their back to the computer is very childish, but great fun.

I found it best not to use a separate room to build the computer, but to spread it all over the house, one bit in each room if I could, just so I knew where everything was.


To my great surprise my lovely wife Judy was completely overjoyed when after only a year, I transferred all the components around the house onto the study wall.


A Warm Glow


The Ena.Computer is designed using 1,100 thermionic triodes. Conveniently each 6N3P electron tube contains 2 triodes around a single heater, halving the physical size and power requirements.

All the double electron tubes are configured as identical NOR gates. The registers are built from groups of 5 NOR gates, and combined into D type flip flops. The NOR gates also form all the other functional components, including the 8 bit ALU, the two oscillators, and the relay drivers.


The amount of heat is ridiculous, but the warm cosy aroma is divine.

The Turner Prize

The Ena.Computer integrates eight large printed circuit boards and three auxiliary PCBs, which combine the electron tubes into a functional computing system. The Graphical user interface, a diode matrix ROM, and a reed relay RAM complete the magic to collectively become an 8 bit electron tube general purpose computer.

It has grown beyond its design, and for me, has become an art installation on the study wall. Indeed, I hope to enter the Ena.Computer for the Turner Prize 2022,


I shall write about the blank canvas of machine code and arty stuff like that, I am sure Tate Modern will be impressed!

The Good, The Bad and The Safety Net

Electron tubes (or just tubes in the USA) are also named thermionic valves (or just valves in the UK). The 6N3P electron tube was produced in Russia in the 1950s and is capable of switching a led on and off over 100 million times a second, which is not bad for a 70 year old.

BANG went two cheap Power Supplies! The Final version of the Ena.Computer now has five second hand AZTEC MP6 PSUs. These professional 60Amp supplies enable the heaters to have a soft start, which hopefully will extend the life of the electron tubes. 

Ena.Computer programs are written using just 16 instructions. Machine code is real code, a totally different world to all the posh high level languages. It's gloves off with no safety net. You simply talk directly to the computer. It's really dangerous and great fun.

Henry's Fibonacci Sequence Video


On 15th August 2021, three months after the first table top run with manual ALU computation and storage, the Ena.Computer was installed on the study wall and demonstrated a clocked, GUI displayed, 8 bit Fibonacci sequence.
The Fibonacci value is displayed vertically, in binary. It uses both the GUI relay memory and NVRAM, and is demonstrated by Henry the cat.


Judy's PONG
Game Video


On 11th January 2022, Judy starred as the “Mysterious black gloved lady” in the epic video production of “PONG Game” and demonstrated a simple version of the game on the Ena.Computer.

Less than 100 machine code instructions make the ball bounce around the court, and subroutines for gameplay and the GUI display complete the program.

It's is a fast, action packed, no holds barred game [NOT], but guess who wins!