Many of the people who make jokes about mainframes wouldn’t know a
System/390 from an AS/400. Here are some tests for figuring out whether
a system is a mainframe:
If you could kill someone by tipping it over on them, it might be a
mainframe.
If the only “mouse” it has is the one living inside it, it might be a
mainframe.
If you need earth-moving equipment to relocate it, it might be a
mainframe.
If it has ever had a card punch designed for it, it might be a
mainframe.
If it weighs more than an RV, it might be a mainframe.
If lights in the neighborhood dim when it’s powered up, it might be a
mainframe.
If its disk platters are big enough to cook pizzas on, it might be a
mainframe.
If keeping all of the manuals together creates a fire hazard, it might
be a mainframe.
If it’s ever been mistaken for a refrigerator (or if the disk drive has
ever been mistaken for a washing machine), it might be a mainframe.
If anyone has ever frozen to death in the room where it’s kept, it might
be a mainframe.
If the operators considered the addition of COBOL to be an upgrade, it
might be a mainframe.
If it was designed before you were born, it might be a mainframe.
If its main power cable is thicker than your neck, it might be a
mainframe.
If the designers have since died from old age, it might be a mainframe.