At a previous job I was receiving training from a Cray engineer and things were winding down as we approached lunch. We were talking about various hardware replacement activities and the instructor recalled such work he had done on older Cray machines, I think it was a Cray-2. My memory is fuzzy around how exactly this came up because upon hearing "So I was replacing a register" my mind detonated. I was aware processors had spanned multiple chips and boards but hadn't really internalised how not long ago that was until that moment.