A large digital computer serving 100-400 users and occupying a special air-conditioned room. At any given point in development of computer technology, the mainframe will be faster, have large main memeory, and be more capable than a minicomputer, which will in turn be faster and more capable than a personal computer. The typical personal computer in 1999 is faster than a mainframe was in 1970. [WordNet 1.5]
The board holding the CPU and the memory forming the central part of a computer to which the peripherals are attached. [WordNet 1.5]