Essentially replaced by PCI.
Macintosh II Introdocution
NuBus, Texas Instruments' synchronous bus definition, allows any device to become master of the system. Therefore, 80286 cards, EtherNet cards, and other intelligent interfaces may, at times, gain control of the CPU. With this architecture, the Macintosh II could run MS-DOS software, act as a smart terminal, or drive a variety of output devices. Apple's NuBus implementation includes interrupt lines from each of the slots, and has changed the size of the interface card to conform to the Macintosh II case size.