While retro computing often focuses on the silicon era, a UK resident known as "Mike" has pushed the boundaries of hardware nostalgia by constructing a functional computer based on vacuum tube technology. Using 460 recycled Soviet-era 6N3P vacuum tubes, Mike has created a system that operates on the most fundamental levels of computing, far removed from the FPGA-based recreations or modern ARM ports seen in recent retro projects.
Architecture and Technical Challenges
The machine is built around NOR gates, a logic choice mirroring the Apollo guidance computers. The hardware consists of 920 thermionic triodes distributed across 46 separate PCBs, which are then mounted on five backplane PCBs. Because the Soviet-era tubes were stored for over 50 years, Mike encountered significant manufacturing inconsistencies. He had to develop a custom test rig because theoretical component values often failed to match the actual performance of these aged tubes.
The system requires between 10 and 15 minutes to stabilize after power-on, generating enough heat to warm the entire room. Due to the random state of the tubes upon startup, a manual reset is required before the machine can execute its limited set of 16 instructions via a 4-bit instruction register.
From Fibonacci to Airships
Currently, the computer is capable of 16-bit math and has been configured to output a 64-bit Fibonacci sequence. However, the ultimate goal is more ambitious: powering a flight simulator for the British R80 airship. The simulation will allow users to control ballast, engine power, and rudder movements through a custom interface.
Since the machine lacks a graphical display, Mike uses a mechanical display—originally a British Rail station clock—to show binary output. This project represents the third such system Mike has built since 2021, driven by what he describes as an "addiction" to the tangible nature of tube-based logic. Given the heat and volatility of the components, he maintains a strict safety protocol, keeping a fire extinguisher nearby to manage the risks associated with these 75-year-old components.
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