UniBone/QBone
From Computer History Wiki
UniBone and QBone are DEC-compatible FLIP CHIP cards which can be simulators for a variety of components (various mass storage peripherals, etc); the former for the UNIBUS (as used in PDP-11/VAX computers), the latter for the QBUS (also in PDP-11/VAX systems).
They emulate CPUs, main memory, several disk subsystems and other peripherals in real time.