A series of large-scale IBM mainframes introduced in 1986. Before the ES/9000 models (System/390), 3090s were the largest mainframes in the System/370 line. Models 120, 150 and 180 are single CPUs. Models 200 through 600 are multiprocessor systems (first digit indicates the number of CPUs). The E, S and J models represent increased speed, respectively. See IBM mainframes.