So back in the 1970s I had a job working on an IBM mainframe computer. Not multicore, no cache or instruction pipeline that I was aware of. A coworker had the i

So back in the 1970s I had a job working on an IBM mainframe computer. Not multicore, no cache or instruction pipeline that I was aware of. A coworker had the idea of writing a timer interrupt to see what kind of instruction was executing at the instance of the interrupt; eventually it accumulated tens of thousand of samples. What kind of instruction was most frequent, was it addition, multiplication, bit-logic, or what? If I remember correctly, at least 90% of the samples were moving data from one place to another (memory-to-memory, register to memory, memory to register, register to register). Computers don't "calculate" most of the time the way I had previously thought. They mostly just rearrange bits, copying this to that.