QBUS was DEC's compact successor to the original UNIBUS architecture, designed primarily for later PDP-11 systems and the MicroVAX family. It multiplexed address and data lines to reduce pin count and system complexity, making it cheaper and easier to implement in smaller systems. QBUS became extremely common in desktop and departmental machines such as the MicroVAX II, MicroVAX 2000, and many PDP-11 models. It supported memory-mapped I/O and DMA, and formed the backbone of many late DEC systems throughout the 1980s.