USSR was using tubes because it was technologically far behind the West (it was still producing cars that were between 30 to even 50 years behind the West) and

USSR was using tubes because it was technologically far behind the West (it was still producing cars that were between 30 to even 50 years behind the West) and was under heavy sanctions. Soviet bloc made chips were actually less reliable and that's one of reasons why commie bloc TTL based computers were so unstable as they had either to import components from the West (see story of Karpiński and his K-202 architecture) if they wanted components that they were allowed to order them in the 1st place or smuggle them (which would not work for large scale) or use inferior in quality components produced within the bloc. Vacuum tubes were much harder to fuck up while production – hence more reliable than commie bloc TTL or LSI. How do I know? I am from one of countries that been in that bloc.