> Bit of an aside but I wonder how far tube technology might have advanced, without semiconductors intervening.
There were Compactrons. There were subminiature vacuum tubes.[1]
A one piece printed circuit board of glass, with multiple tubes, might be possible.
A glass plate made with lots of recesses, electrodes and wiring created by photo-etching like printed circuit boards, a glass plate on top, pumped down to vacuum and sealed. A low-density integrated tube.
That's what a plasma panel display is. It's an integrated array of neon lamps. In a vacuum fluorescent display, each illuminated element is a triode vacuum tube. So it's quite possible to fabricate a big array of tubes.
Maybe something like a ball grid array would work for external connections.
Probably could have been done if necessary. Density probably would have maxed out around the density of elements on on the most dense vacuum fluorescent displays. Maybe devices at 1mm scale, or 1,000,000 nm. Good enough for mainframes and minicomputers, but not microprocessors.
There were Compactrons. There were subminiature vacuum tubes.[1]
A one piece printed circuit board of glass, with multiple tubes, might be possible. A glass plate made with lots of recesses, electrodes and wiring created by photo-etching like printed circuit boards, a glass plate on top, pumped down to vacuum and sealed. A low-density integrated tube.
That's what a plasma panel display is. It's an integrated array of neon lamps. In a vacuum fluorescent display, each illuminated element is a triode vacuum tube. So it's quite possible to fabricate a big array of tubes.
Maybe something like a ball grid array would work for external connections.
Probably could have been done if necessary. Density probably would have maxed out around the density of elements on on the most dense vacuum fluorescent displays. Maybe devices at 1mm scale, or 1,000,000 nm. Good enough for mainframes and minicomputers, but not microprocessors.
[1] https://archive.org/details/The_MIT_Museum_The_Subminiature_...