NuBus
Encyclopedia
NuBus is a 32-bit
32-bit
The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....

 parallel computer bus
Computer bus
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...

, originally developed at MIT
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...

 as a part of the NuMachine
NuMachine
The NuMachine was developed in the late 1970s atMIT's Laboratory for Computer Science by Professor Steve Ward and his research group in concert with Western Digital. It was a project to design a computer workstation that interfaced with local area networks using microprocessors...

workstation
Workstation
A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems...

 project. The first complete implementation of the NuBus and the NuMachine was done by Western Digital
Western Digital
Western Digital Corporation is one of the largest computer hard disk drive manufacturers in the world. It has a long history in the electronics industry as an integrated circuit maker and a storage products company. Western Digital was founded on April 23, 1970 by Alvin B...

 for their NuMachine, and for the Lisp Machines Inc. LMI-Lambda. The NuBus was later incorporated in products by Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

 (Explorer
TI Explorer
The Texas Instruments Explorer is a family of Lisp Machine computers. These computers were sold by Texas Instruments in the 1980s. The Explorer is based on a design from Lisp Machines Incorporated, which is based on the MIT Lisp Machine....

), Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...

 and NeXT
NeXT
Next, Inc. was an American computer company headquartered in Redwood City, California, that developed and manufactured a series of computer workstations intended for the higher education and business markets...

. It is no longer widely used outside of the embedded market.

Architecture

NuBus was a considerable step forward compared to other interfaces of the day. At the time most computer bus systems were 8-bit, as were the computers they plugged into. However, NuBus decided on a 32-bit interface because it was clear the market was headed in that direction.

In addition, NuBus was agnostic about the processor itself. Most buses up to this point were basically the pins on the CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 run out onto the backplane
Backplane
A backplane is a group of connectors connected in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a complete...

, meaning that the cards had to conform to the signalling and data standards of the machine they were plugged into (being little endian for instance). NuBus made no such assumptions, which meant that a NuBus card could be plugged into any NuBus machine, as long as there was an appropriate device driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....

.

In order to select the proper device driver, NuBus included an ID scheme that allowed the cards to identify themselves to the host computer during startup. This meant that the user didn't have to configure the system, the bane of bus systems up to that point. For instance, with ISA
Industry Standard Architecture
Industry Standard Architecture is a computer bus standard for IBM PC compatible computers introduced with the IBM Personal Computer to support its Intel 8088 microprocessor's 8-bit external data bus and extended to 16 bits for the IBM Personal Computer/AT's Intel 80286 processor...

 the driver had to be configured not only for the card, but for any memory it required, the interrupt
Interrupt
In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....

s it used, and so on. NuBus required no such configuration, making it one of the first examples of plug-and-play
Plug-and-play
In computing, plug and play is a term used to describe the characteristic of a computer bus, or device specification, which facilitates the discovery of a hardware component in a system, without the need for physical device configuration, or user intervention in resolving resource conflicts.Plug...

architecture.

On the downside, while this flexibility made NuBus much simpler for the user and device driver authors, it made things more difficult for the designers of the cards themselves. Whereas most "simple" bus systems were easily supported with a handful of input/output
Input/output
In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...

 chips designed to be used with that CPU in mind, with NuBus every card and computer had to convert everything in a platform-agnostic "NuBus world". Typically this meant adding a NuBus controller chip between the bus and any I/O chips on the card, increasing costs. While this is a trivial exercise today, one that all newer buses require, at the time in the 1980s NuBus was considered complex and expensive.

Implementations

The NuBus became a standard in 1987 as IEEE 1196. This version used a standard 96-pin three-row connector, running the system on a 10 MHz clock for a maximum burst throughput of 40 MB/s and average speeds of 10 to 20 MB/s. A later addition, NuBus90, increased the clock rate to 20 MHz for better throughput, burst increasing to about 70 MB/s, and average to about 30 MB/s.

The NuBus was first developed commercially in the Western Digital NuMachine, and first used in a production product by their licensee, Lisp Machines, Inc., in the LMI-Lambda, a Lisp Machine
Lisp machine
Lisp machines were general-purpose computers designed to efficiently run Lisp as their main software language. In a sense, they were the first commercial single-user workstations...

. The project and the development group was sold by Western Digital to Texas Instruments in 1984. The technology was incorporated into their TI Explorer
TI Explorer
The Texas Instruments Explorer is a family of Lisp Machine computers. These computers were sold by Texas Instruments in the 1980s. The Explorer is based on a design from Lisp Machines Incorporated, which is based on the MIT Lisp Machine....

, also a Lisp Machine
Lisp machine
Lisp machines were general-purpose computers designed to efficiently run Lisp as their main software language. In a sense, they were the first commercial single-user workstations...

. In 1986, Texas Instruments used the NuBus in the S1500 multiprocessor UNIX system. Later, both Texas Instruments and Symbolics
Symbolics
Symbolics refers to two companies: now-defunct computer manufacturer Symbolics, Inc., and a privately held company that acquired the assets of the former company and continues to sell and maintain the Open Genera Lisp system and the Macsyma computer algebra system.The symbolics.com domain was...

 developed Lisp Machine NuBus boards (the TI MicroExplorer and the Symbolics MacIvory) based on their Lisp supporting microprocessors. These NuBus boards were co-processor Lisp Machines for the Apple Macintosh
Macintosh
The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

 line (the Mac II and Mac Quadras).

NuBus was later selected by Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...

 for use in their Macintosh II
Macintosh II
The Apple Macintosh II was the first personal computer model of the Macintosh II series in the Apple Macintosh line and the first Macintosh to support a color display.- History :...

 project, where its plug-n-play nature fit well with the Mac philosophy of ease-of-use. It was used in most of the Macintosh II series
Macintosh II series
The Macintosh II series was a series of personal computers in Apple's Macintosh line.-Features:Unlike prior Macintosh models, which were all compact Macintosh designs, the Macintosh II models were "modular" systems which did not include built-in monitors and were expandable...

 and Macintosh Quadra
Macintosh Quadra
The Macintosh Quadra series was Apple Computer's product family of professional high-end Apple Macintosh personal computers built using the Motorola 68040 CPU. The first two models in the Quadra line were introduced in 1991, and the name was used until the Power Mac was introduced in 1994...

s that made up the professional-level Mac lineup from the late 1980s into the mid-1990s, and was upgraded to NuBus90 starting with the Macintosh Quadra
Macintosh Quadra
The Macintosh Quadra series was Apple Computer's product family of professional high-end Apple Macintosh personal computers built using the Motorola 68040 CPU. The first two models in the Quadra line were introduced in 1991, and the name was used until the Power Mac was introduced in 1994...

s. Early Quadras only supported the 20 MHz rate when two cards were talking to each other, since the motherboard controller was not upgraded. This was later addressed in the 660AV and 840AV models, and used on the early PowerMac models. Later PowerMacs adopted Intel's PCI
Peripheral Component Interconnect
Conventional PCI is a computer bus for attaching hardware devices in a computer...

 bus. Apple's NuBus implementation used pin and socket connectors with thumbscrews on the back of the card rather than the often stubborn edge connector
Edge connector
An edge connector is the portion of a printed circuit board consisting of traces leading to the edge of the board that are intended to plug into a matching socket. The edge connector is a money-saving device because it only requires a single discrete female connector , and they also tend to be...

s with Phillips screws inside the case that most cards use, making it much easier to install cards. Apple's computers also supplied an always-on +5 V "trickle" power supply for tasks such as watching the phone line while the computer was turned off. This was apparently part of an unapproved NuBus standard.

NuBus was also selected by NeXT Computer
NeXT Computer
The NeXT Computer was a high-end workstation computer developed, manufactured and sold by Steve Jobs' company NeXT from 1988 until 1990. It ran the Unix-based NeXTSTEP operating system. The NeXT Computer was packaged in a 1-foot die-cast magnesium cube-shaped case, which led to the machine being...

 for their line of machines, but used a different physical PCB
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

 layout. NuBus appears to have seen little use outside these roles, and when Apple switched to PCI
Peripheral Component Interconnect
Conventional PCI is a computer bus for attaching hardware devices in a computer...

 in the mid 1990s, NuBus quickly disappeared.

See also

  • Amiga Zorro II  (Amiga Autoconfig
    Autoconfig
    Autoconfig is an auto-configuration protocol of Amiga computers which is intended to automatically assign resources to expansion devices without the need for jumper settings...

     bus)
  • Industry Standard Architecture
    Industry Standard Architecture
    Industry Standard Architecture is a computer bus standard for IBM PC compatible computers introduced with the IBM Personal Computer to support its Intel 8088 microprocessor's 8-bit external data bus and extended to 16 bits for the IBM Personal Computer/AT's Intel 80286 processor...

      (ISA)
  • Extended Industry Standard Architecture
    Extended Industry Standard Architecture
    The Extended Industry Standard Architecture is a bus standard for IBM PC compatible computers...

     (EISA)
  • Micro Channel architecture
    Micro Channel architecture
    Micro Channel Architecture was a proprietary 16- or 32-bit parallel computer bus introduced by IBM in 1987 which was used on PS/2 and other computers through the mid 1990s.- Background :...

     (MCA)
  • VESA Local Bus
    VESA Local Bus
    The VESA Local Bus was mostly used in personal computers. VESA Local Bus worked alongside the ISA bus; it acted as a high-speed conduit for memory-mapped I/O and DMA, while the ISA bus handled interrupts and port-mapped I/O.-Historical overview:In the early 1990s, the I/O bandwidth of...

     (VESA)
  • Peripheral Component Interconnect (PCI)
  • Accelerated Graphics Port
    Accelerated Graphics Port
    The Accelerated Graphics Port is a high-speed point-to-point channel for attaching a video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics. Since 2004 AGP has been progressively phased out in favor of PCI Express...

     (AGP)
  • PCI Express
    PCI Express
    PCI Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP bus standards...

     (PCIe)
  • List of device bandwidths

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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