Apple Attachment Unit Interface
Encyclopedia
Attachment Unit Interface
An Attachment Unit Interface is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit , sometimes known as a transceiver. It is the part of the IEEE Ethernet standard located between the Media Access Control , and the MAU...
(AUI) used to connect Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...
s to computer equipment. AUI was popular in the era before the dominance of 10BASE-T
10BASE-T
Ethernet over twisted pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. Other Ethernet cable standards employ coaxial cable or optical fiber. Early versions developed in the 1980s included StarLAN followed by 10BASE-T. By the 1990s, fast, inexpensive...
networking that started in the early 1990s; AAUI was an attempt to make the connector much smaller and more user friendly.
FriendlyNet
AAUI was part of a system of Ethernet peripherals that tried to make connecting to Ethernet much easier. At the time, Ethernet systems usually were 10BASE210BASE2
10BASE2 is a variant of Ethernet that uses thin coaxial cable , terminated with BNC connectors...
, also known as thinnet. Apple's system was called FriendlyNet. A FriendlyNet 10BASE2 system did not use BNC T-connectors or separate 50 Ω
Ohm
The ohm is the SI unit of electrical resistance, named after German physicist Georg Simon Ohm.- Definition :The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere,...
terminators
Electrical termination
Electrical termination of a signal involves providing a terminator at the end of a wire or cable to prevent an RF signal from being reflected back from the end, causing interference...
. Instead of a single BNC connector
BNC connector
The BNC connector ' is a common type of RF connector used for coaxial cable. It is used with radio, television, and other radio-frequency electronic equipment, test instruments, video signals, and was once a popular computer network connector. BNC connectors are made to match the characteristic...
that was inserted into a T-connector placed inline in the cable, the AAUI transceiver had two BNC connectors, one on each side to which the cables were attached. The transceiver would automatically terminate the network if a cable was not attached to one of the sides. Additionally, Apple 10BASE2 cables would terminate the network if no device was attached to them. Thus the number of mistakes that could be made hooking up a thinnet network was reduced considerably. Since any of these mistakes would disable the network in an area this was a significant improvement.
FriendlyNet equipment was quite expensive and even third party AAUI transceivers were rather expensive. Because of this, Apple's computers, which were billed as having built-in Ethernet, were actually rather expensive to connect to Ethernet, perhaps adding as much as 10% to the total price of the computer system. Additionally, AAUI held no advantage for any system other than 10BASE2 and thus as 10BASE-T became ubiquitous it became impossible to justify the cost of an external transceiver at all. Apple eventually abandoned the system and sold off the name.
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...
, Centris
Macintosh Centris
Macintosh Centris is a line of Macintosh computers, introduced in 1993, that were built around the Motorola 68LC040 and 68040 CPUs. The name was chosen to indicate that the consumer was selecting a Macintosh in the center of Apple's product line: lower performance than the Quadra computers, but...
, PowerBook 500, Duo Dock II (for PowerBook Duo)
PowerBook Duo
The PowerBook Duo was a line of small subnotebooks manufactured and sold by Apple Computer from 1992 until 1997 as a more compact companion to the PowerBook line. Improving upon the PowerBook 100's portability , the Duo came in seven different models...
and early Power Macintosh
Power Macintosh
Power Macintosh, later Power Mac, was a line of Apple Macintosh workstation-class personal computers based on various models of PowerPC microprocessors that were developed, marketed, and supported by Apple Inc. from March 1994 until August 2006. The first models were the Power Macintosh 6100,...
es had an AAUI port, which requires an external transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...
. By the time AAUI was nearing the end of its life, an AAUI transceiver could cost as much or more than the cost of a low-cost Ethernet card on the PC. Later models included both an AAUI and modular connector port for directly connecting 10BASE-T; either could be used, but not both at the same time. AAUI connectors were also present on some Processor Direct Slot
Processor Direct Slot
Processor Direct Slot or PDS introduced by Apple Computer, in several of their Macintosh models, provided a limited measure of hardware expandibility, without going to the expense of providing full-fledged bus expansion slots.Typically, a machine would feature multiple bus expansions slots, if any...
Ethernet adapter cards used in Macintosh LC
Macintosh LC
The Macintosh LC was Apple Computer's product family of low-end consumer Macintosh personal computers in the early 1990s. The original Macintosh LC was released in 1990 and was the first affordable color-capable Macintosh. Due to its affordability and Apple II compatibility the LC was adopted...
and Performa
Macintosh Performa
The Macintosh Performa series was Apple Computer's consumer product family of Apple Macintosh personal computers sold through department stores and mass-market retailers from 1992 until 1997, when it was superseded by the Power Macintosh 5x00 series...
machines. AAUI had disappeared by the late 1990s, when all new Apple machines included only 10BASE-T.
Third party vendors
Many third parties also created AAUI transceivers. Most made simplifications to the connectors and cables, presumably to reduce costs. Most third parties, as well as any non-Apple equipment would use standard 10BASE2 cabling, including T-connectors and manual termination. Additionally, Apple's 10BASE2 cables were not really feasible for all uses since they only came in fixed lengths and the ends were not detachable, making it very difficult to wire them through walls. Unfortunately, when mixing and matching Apple and non-Apple 10BASE2 devices, there were many seemingly natural configurations of cables and connectors which would cause the network to become unreliable or unusable in the area, reducing the value of the complex and proprietary Apple 10BASE2 wiring system.Connector and signals
AUI used a full-sized 15-pin D connectorD-subminiature
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smaller connectors used on computer systems....
(model DA-15) that used a sliding clip for mechanical connections in place of thumbscrews. AAUI replaced these with a small 14-position, 0.050-inch-spaced ribbon contact connector. The connector may have been changed to avoid confusion with the monitor port on early 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...
es, which also used a 15-pin D connector. The connector was locked into position using two clips or hooks on the sides of the connector outside of the D shell (where screws often are on D subs) which automatically clicked on when plugged in, and could be removed simply by pulling back on a sliding sheath over the body of the connector, disengaging the hooks. 3rd party AAUI devices often omitted this sheath, requiring the user to directly squeeze small tabs on the sides of the plug housing to detach the hooks.
AAUI signals have the same description, function, and electrical requirements as the Attachment Unit Interface
Attachment Unit Interface
An Attachment Unit Interface is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit , sometimes known as a transceiver. It is the part of the IEEE Ethernet standard located between the Media Access Control , and the MAU...
(AUI) signals of the same name, as detailed in IEEE 802.3
IEEE 802.3
IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications...
-1990 CSMA/CD Standard, section 7, with the exception that most hosts provide only 5 volt power rather than the 12 volts required for most AUI transceivers. An adapter containing a power supply
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
to provide the required 12 volts was available from Apple to permit connection of standard AUI transceivers to an AAUI port - this facilitated direct connection to 10BASE-F
10BASE-FL
10BASE-FL is the most commonly used 10BASE-F specification of Ethernet over optical fiber. It replaces the original fiber-optic inter-repeater link specification, but retains compatibility with FOIRL-based equipment...
(fibre optic) and 10BASE5
10BASE5
10BASE5 was the original commercially available variant of Ethernet.For its physical layer it used cable similar to RG-8/U coaxial cable but with extra braided shielding. This is a stiff, diameter cable with an impedance of 50 ohms , a solid center conductor, a foam insulating filler, a shielding...
(ThickNet) Ethernet networks, for which AAUI transceivers were not available.
| Pin | Signal Name | Signal Description |
|---|---|---|
| 1 | FN Pwr | Power (+12 V @ 2.1 W or +5 V @ 1.9 W) |
| 2 | DI-A | Data In circuit A |
| 3 | DI-B | Data In circuit B |
| 4 | Vcc VCC VCC may refer to:as a three-letter acronym:* Common-collector voltage , plus collector supply line voltage in a common NPN circuit.* Vale of Catmose College, an arts college in England.* Valencia Community College, in Orlando, Florida... |
Voltage Common |
| 5 | CI-A | Control In circuit A |
| 6 | CI-B | Control In circuit B |
| 7 | ||
| 8 | Secondary +5 volts (from host) | |
| 9 | DO-A | Data Out circuit A |
| 10 | DO-B | Data Out circuit B |
| 11 | Vcc | Secondary Voltage Common |
| 12 | NC | Reserved |
| 13 | NC | Reserved |
| 14 | FN Pwr | Secondary +12 V @ 2.1 W or +5 V @ 1.9 W |
| Shell | Protective Gnd | Protective Ground |
See also
- HardwareHardwareHardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
- Computer networkComputer networkA computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....