>"My understand is the Burroughs series of mainframes were designed to support user definable instruction sets so that a computing site would be optimized for s

>"My understand is the Burroughs series of mainframes were designed to support user definable instruction sets so that a computing site would be optimized for specific workloads and languages." This is fascinating although I'm having trouble wrapping my head around it. Would "user" here be an engineer or field tech from Burroughs or mainframe admin at the company the was leasing the Burroughs system. You would have to have very intimate knowledge of CPU architecture to sort of roll you own instruction set no? Or am I misunderstanding this and it would be more about removing some inefficient instructions for a specific type of workload?