mainframe

nouns

a large digital computer serving 100-400 users and occupying a special air-conditioned room
mainframe, mainframe computer
(computer science) the part of a computer (a microprocessor chip) that does most of the data processing
"the CPU and the memory form the central part of a computer to which the peripherals are attached"
C.P.U., CPU, central processing unit, central processor, mainframe, processor