NuBus
| Year created | 1987 |
|---|---|
| Created by | MIT |
| Width in bits | 32 |
| Style | Parallel |
NuBus (pron. 'New Bus') is a 32-bit parallel computer bus, originally developed at MIT and standardized in 1987 as a part of the NuMachine workstation project. The first complete implementation of the NuBus was done by Western Digital for their NuMachine, and for the Lisp Machines Inc. LMI Lambda. The NuBus was later incorporated in Lisp products by Texas Instruments (Explorer), and used as the main expansion bus by Apple Computer and NeXT. It is no longer widely used outside the embedded market.
Early microcomputer buses like S-100 were often just connections to the pins of the microprocessor and to the power rails. This meant that a change in the computer's architecture generally led to a new bus as well. Looking to avoid such problems in the future, NuBus was designed to be independent of the processor, its general architecture and any details of its I/O handling.
Among its many advanced features for the era, NuBus used a 32-bit backplane when 8- or 16-bit busses were common. This was seen as making the bus "future-proof", as it was generally believed that 32-bit systems would arrive in the near future while 64-bit buses and beyond would remain impractical and excessive.
In addition, NuBus was agnostic about the processor itself. Most buses up to this point conformed to the signalling and data standards of the machine they were plugged into (being big or little endian for instance). NuBus made no such assumptions, which meant that any NuBus card could be plugged into any NuBus machine, as long as there was an appropriate device driver.
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