The things that have to be considered when 'upgrading' those legacy systems are, what language were the programs written in - who programs directly in assembler today and how does the system interface with the real world - in industrial systems that can be through custom interface cards that are no longer made but the machine tools have a life of 25 to 50 years more.
When you mention such things to management and the bean counters they go all quiet for some strange reason.
Biting the hand that feeds IT
