I’ve never worked with major enterprise or government systems where there’s aging mainframes — the type that get parodied for running COBOL. So, I’m completely ignorant, although fascinated. Are they power hogs? Are they wildly cheap to run? Are they even run as they were back in the day?
I don’t know the exact numbers but: I frequently used a VAX11/780. Its main components were two enclosures (CPU and Memory), each about a square meter in footprint and somewhere in the range of 1.6m high (IIRC). Both had their power delivered as 3x380V (i.e. European three-phase power) into the power supply part (the lower half to 2/3rds of those blocks) which turned it into rock solid 5V - and a LOAD of heat, which meant the room also needed some extra strong AC.
That thing was an 8MHz cpu with 8MB of RAM.