NuBus

NuBus is a parallel 32- bit bus, which was originally developed as part of the NuMachine workstation project at MIT and temporarily used by Apple Computer, NeXT Computer and Texas Instruments. It is now rarely used.

NuBus architecture

NuBus was a significant step forward compared to other interfaces in its time. As most bus systems were still 8 bits wide (including the computer, where they were used ), it was decided to introduce a 32 -bit interface with the NuBus, since it was clear that the market would develop in this direction.

The NuBus was working relatively independently of the processor itself Most bus systems until now were simple lines that went from the CPU to the backplane. This meant that the expansion cards with the standard data of the processor had to stand in line (eg Little Endian). When NuBus is different. The expansion cards to be run in each NuBus computers, provided that a suitable instrument driver is available.

Thus, it is possible to select a suitable device driver, the NuBus an ID scheme is used to identify the extension cards at startup. Additionally, the user no longer needs to configure the system as it was in other systems this time yet. For example, not only the driver of the expansion card must be selected at the ISA bus, but it must also storage areas and interrupts the card can be specified. The NuBus does not expect such a configuration, by which he is one of the first examples of a plug-and- play architecture.

Although the NuBus in many fields represented a simplification in the handling of hardware changes to the development of expansion cards is complicated for the manufacturer. To provide compatibility, each expansion card had a corresponding NuBus controller chip accommodation, whereby the manufacturing costs of the expansion card increased. While nowadays such technique is hardly indispensable, the NuBus in the 1980s was seen as complex and expensive.

NuBus applications

The NuMachine was never published, however, Texas Instruments, technology has taken over in 1980 and later can standardize as IEEE 1196. This version used a three-row 96 -pin connector, which is also used in other systems such as VME and PCI. A system with 10 MHz bus speed was a maximum data rate of 37.5 MB / s burst transfer ( or an average of about 10 to 20 MB / s) reach. At a subsequent change NuBus90, the clock rate was increased to 20 MHz to accelerate the data rate to a maximum of about 75 MB / s (on average about 30 MB / s).

NuBus was first used in the Lambda Lisp Machine by LMI. Texas Instruments licensed the design of the LMI Lambda Lisp Machine and published its own version, the TI Explorer. The LMI Lambda based on the design work of the MIT Lisp Machine NuMachine and MIT. A short time later, in 1986, Texas Instruments has the NuBus used in his S1500 multiprocessor UNIX system.

Apple Computer has followed the NuBus for the Macintosh II project chosen because this was a perfect fit with plug- n-play in the " Easy to use " philosophy of Apple. This was in most Macs from late 1980, into, used in the 1990s.

NuBus90 was first inserted into the Macintosh Quadras. The first Quadras supported only the 20 MHz variant if two expansion cards communicating with each other, since the motherboard controller was not upgraded. This was later changed in the 660AV and 840AV models and incorporated into the first PowerMac models. The implementation of Apple offered in addition to a permanent 5 V line, so expansion cards can fulfill additional tasks (such as call monitoring the telephone line ), while the computer was turned off. This change was not provided in the NuBus standard.

NuBus was also used by NeXT Computer, but with a different layout as the printed circuit board. NuBus was hardly more widespread than it was displaced mid-1990s through the PCI bus.