Apple Computer NUbus
Connector Pinout



Apple NuBus Description

This page describes the pinout and signal names for NuBus as used on Apple computers [Macintosh and NeXT Computer].
The NUbus expansion interface is obsolete and should not be used for new designs. NUbus is a 32-bit bus and was defined by IEEE Std 1196-1987.
NuBus was used as an Apple expansion bus with 32 bit address and 32 bit data bus operating at 10MHz, with a throughput of 40MBps.
The NuBus card had a form factor of 12" x 7", and used a standard 96-pin three-row (VME) connector.
NuBus90, increased the clock rate to 20Mhz providing a throughput of 70Mbps. NUbus was replaced by the PCI expansion bus.

Additional pinout tables for other Apple protocols are listed on the Apple Computer Buses page.
A full list of buses found on any computer type is listed on the Personal Computer Buses page.
Any other style of electrical interface may be found by using the 'Buses' icon at the bottom of the page.




Row A Signals
Pin # Signal name Signal
Description
1 -12 V -12 VDC
2 -  
3 /SPV System Parity Valid
4 /SP System Parity
5 /TM1 Transfer Mode 1
6 /AD1 Address/Data 1
7 /AD3 Address/Data 3
8 /AD5 Address/Data 5
9 /AD7 Address/Data 7
10 /AD9 Address/Data 9
11 /AD11 Address/Data 11
12 /AD13 Address/Data 13
13 /AD15 Address/Data 15
14 /AD17 Address/Data 17
15 /AD19 Address/Data 19
16 /AD21 Address/Data 21
17 /AD23 Address/Data 23
18 /AD25 Address/Data 25
19 /AD27 Address/Data 27
20 /AD29 Address/Data 29
21 /AD31 Address/Data 31
22 GND Ground
23 GND Ground
24 /ARB1 Arbitrate 1
25 /ARB3 Arbitrate 3
26 /ID1 Slot ID 1
27 /ID3 Slot ID 3
28 /ACK Acknowledge
29 +5 V +5 VDC
30 /RQST Bus Request
31 /NMRQ  
32 +12 V +12 VDC
Row B Signals
Pin # Signal name Signal
Description
1 -12 V -12 VDC
2 GND Ground
3 GND Ground
4 +5 V +5 VDC
5 +5 V +5 VDC
6 +5 V +5 VDC
7 +5 V +5 VDC
8 Unused Reserved
9
10
11
12 GND Ground
13
14
15
16
17
18
19
20
21
22
23
24 Unused Reserved
25
26
27
28 +5 V +5 VDC
29 +5 V +5 VDC
30 GND Ground
31 GND Ground
32 +12 V +12 volts
Row C Signals
Pin # Signal name Signal
Description
1 /RESET Board Reset
2 -  
3 +5 V +5 VDC
4 +5 V +5 VDC
5 /TM0 Transfer Mode 0
6 /AD0 Address/Data 0
7 /AD2 Address/Data 2
8 /AD4 Address/Data 4
9 /AD6 Address/Data 6
10 /AD8 Address/Data 8
11 /AD10 Address/Data 10
12 /AD12 Address/Data 12
13 /AD14 Address/Data 14
14 /AD16 Address/Data 16
15 /AD18 Address/Data 18
16 /AD20 Address/Data 20
17 /AD22 Address/Data 22
18 /AD24 Address/Data 24
19 /AD26 Address/Data 26
20 /AD28 Address/Data 28
21 /AD30 Address/Data 30
22 GND Ground
23 /PFW  
24 /ARB0 Arbitration 0
25 /ARB2 Arbitration 2
26 /ID0 Slot ID 0
27 /ID2 Slot ID 2
28 /START  
29 +5 V +5 VDC
30 +5 V +5 VDC
31 GND Card Ground
32 /CLK Board Clock



The slash before each of the signal names indicate that the line is active low.
This pinout table provides the signal assignments for a data bus that is over 25 years old. The electrical interface went obsolete after the PCI bus was released in 1991. So unless your debugging a 20 year old computer, this data should not be used.

FYI; The terms Signal Assignments, Pinout, and Pin Out all mean the same thing. They each define which bus signal resides on which pin in the interface, and the terms are interchangeable.

Nubus was also released by TI in 1983, before it became an IEEE standard. The two interfaces are not the same.
Nubus is obsolete and should not be used for new designs, use the PCIe Interface as an upgrade path.

There are no companies that have been identified that produce components or ICs for the NuBus interface, because the bus is out-dated. However this site does include a generic listing of component manufacturers, as; Component and Semiconductor Manufacturers [alphabetic listing].

NuBus is an Out-dated, legacy interface for peripherals and other printer interfaces.
However judging by the page views or searches, interest in this Obsolete interface has faded.
Apple has moved on to the same buses and standard interfaces found in normal PCs, once called IBM compatible machines.




This expansion bus went obsolete over 20 years ago, and should no longer be used.
The data remains for informational reasons only and provides no value to modern expansion board design.
Although a Legacy system may still use the Interface Bus.
The NuBus is Obsolete and should not be used with new system designs, use the PCIe Interface as an upgrade path. Additional PC Buses for reference.
Do not reference this bus in new designs, the NuBus interface is Antiquated and has been obsolete for a number of years now. However, in it's day, NuBus was considered a fast interface bus. The NuBus interface is obsolete and should not be used in up-coming designs. Apple Computer no longer supports the NuBus interface.

Pinout tables for other Apple protocols are listed here; Apple Computer Buses.


Topic Navigation: Engineering Home > Interface Buses > Personal Computer Buses > Apple Computer Buses > NUBus.


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Modified 7/18/2015
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