How would the development of computers be altered by the time of the 1960s & 1970s if we only figured out a practical way to synthesise silicon crystals usable for silicon transistors after that time frame?

this is meant to be a more sound version of a different question i made hopefully better thought out than the last one taking into consideration the top answer for it. I'm not just editing that one because i think it's different enough & there's already an answer with 11 votes that would make not sense if i edited it.

For the purposes of the question, instead of no one just thinking of them, a practical method for the synthesis of pure enough silicon crystals isn't figured out until far later, roughly the late 1970s. Up until that point there is little to no divergence in the development of computers How would this affect how computers develop into the 1960s & 1970s when only different materials are available? What would take the place of silicon transistors & how would that limit computing?

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    $\begingroup$ So no radar developments to drive the need for high quality diodes? (This is what led to the development of the Si purification process still used today.) $\endgroup$
    – Jon Custer
    Jun 17 at 14:36

2 Answers 2


The earliest transistors were discrete 'cat's whisker' devices - crystals with a gold contact on a crystal of copper oxide, or something like that. The manufacturing for integrated circuits is a different sort of thing, which many devices being written to the same slice of crystal. The techniques for growing the crystals are very similar, so I would not see a plausible way in which Silicon circuits are hard to make, but Gallium Arsenide is easy. I think if we are wanting to make an alternative technology for the 1980's we would have to look at something else that was easier to make.

A neon bulb can operate at 5V, but may need 20V to strike the arc. If you have a grid of neon lamps powered at 10 volts, and you provide an extra +5V on one row and an extra +5v on on e column you can strike or extinguish the lamp on that intersection. This is how a monochrome plasma display used to work in the 1980's. Some of them had several bits stacked deep to give grey levels. I particularly remember a 4-level one in about 1986 that gave 16 shades of neon pink. This was a lot of memory in the day, and some computers allowed you to read the state back from the display bits. it is a sort of 3-D integrated valve.

Instead of supposing silicon integrated circuits were hard to make, let us suppose the something else was easier. It is possible that the early history of computing could have done a different way if similar photoresist and etch techniques were used to make integrated valves. We know the plasma display worked. There is no reason why people could not have made a microprocessor using the same technologies. As you shrink the device, the maximum clock rate goes up. There would have been a minimum size for the neon arc, so you would never get the densities of the silicon circuit. Sooner or later, they would have to make the jump to silicon, but it might have happened as late as the 1980's.


Let's suppose that, for one reason or another, the transistor never came about at all. How far can we take computing?

1936 - Zuse Z1 is a fully mechanical computing machine, using sliding parts for memory and linkages for logic gates.

1941 - Zuse Z3 uses electromechanical relays for logic, valves for memory.

1942 - A capacitor-based form of memory is patented.

1947 - development of magnetic drum memory.

1949 - Following a conference organised by John von Neumann architecture, EDSAC and CSIRAC are completed using valves for logic, ultrasonic 'echoes' in mercury lines for fast memory.

Arguably one of the most advanced computers that did not make use of silicon was BESK (1953-1966) using germanium diodes, vacuum tubes and magnetic drum memory. After this point, essentially all computers in our timeline were transistorised. Reliable, small, power-efficient transistors effectively killed any motive to further develop valves. As we are just now beginning to discover, tubes were not a technical dead end - in fact, they may offer some advantages over semiconductor technology in the future. A speculative alternate timeline runs:

1955 - vacuum tubes continue to be miniaturised. John Von Neumann suggests including multiple tubes into a single package with a common heater coil, inventing the integrated circuit.

1959 - The vacuum fluorescent display is developed by Phillips, setting the stage for metal-in-glass package development with small-scale features. A smaller line of specialised computing packages is developed alongside VFDs for commercial and military computers.

1959 - development of the cold-cathode tube dramatically improves power consumption, as unheated filaments become usable for calculation.

late 1960's - photoresist-based manufacturing becomes well-understood enough to make small features. Cost of computers begins to fall, as more valves can now be squeezed in to less space.

1977 - Discovery of scandium-doped cathodes, which give good valve performance even at comparatively low temperature, dramatically improves power efficiency of valves.

1970's - Vacuum-channel transistors become reliable enough to replace magnetic core memory in computer ram. Clock speeds increase dramatically, but it proves somewhat difficult to scale up the number of transistors due to the slow development cycle of sealing things into glass packages.

1980's - Nanofabrication technology, combined with improved cathode materials becomes good enough to create valves small enough to avoid the need for a vacuum entirely.

1990's - First consumer-grade computers. Uptake is limited by the manufacturing costs of these rather niche components, combined with limited component lifespan due to inevitable failure of the small features with regular use.

These microvalve-based computers would have an number of disadvantages compared to transistorised computers, mainly to do with power and failure modes. I imagine the jump to mobile devices would take much longer without silicon, but we will never know - given good motivation, technology has a habit of flowing around obstacles rather than being stopped by particular roadblocks. By 1950, the usefulness and need for computers was already considered self-evident by experts, and it is virtually certain that the redirecting the money and effort thrown at semiconductors in the '60s and '70s and to vacuum tubes would quite likely have resulted in equally impressive improvements in performance and reliability.


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