It depends on the application. Some use an unconventional process because of application requirements e.g. radiation hardening. Special purpose fabs are often s

It depends on the application. Some use an unconventional process because of application requirements e.g. radiation hardening. Special purpose fabs are often subsidized to some extent to keep them running. Also, the US military will upgrade the silicon of existing systems if the situation warrants it e.g. it is cheaper to use more modern silicon than to maintain a fab for the old silicon. Most weapon systems use old silicon that needs to be robust in all military operational environments. They don't benefit from having more modern silicon. Terminal guidance systems on hypersonic missiles that do kinetic intercept of other hypersonic missiles often use something like a MIPS R3000/4000 class CPU and a DSP of similar vintage. ISR systems (intelligence, surveillance, reconnaissance) benefit from state-of-the-art silicon because that data is extremely large and analysis is time sensitive. Since pervasive ISR at scale is a cornerstone of modern military operations, having the best silicon and software for this type of computation is strategic. In these cases, it is often the latest commodity silicon.