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?
Mainframes are basically large rack mounted computers, and typically require many kW of power to run.
They’re still selling mainframes. A new IBM z16 takes 3-phase power and can use up to 30kW, or about 1,000 times a typical laptop.