History[ edit ] An IEEE pin female on a circuitboard In the s, Centronics developed the now-familiar printer parallel port that soon became a de facto standard. Centronics had introduced the first successful low-cost seven-wire print head[ citation needed ], which used a series of solenoids to pull the individual metal pins to strike a ribbon and the paper. A dot matrix print head consists of a series of metal pins arranged in a vertical row. Each pin is attached to some sort of actuator, a solenoid in the case of Centronics, which can pull the pin forward to strike a ribbon and the paper.
An early computer might contain a hand-wired CPU of vacuum tubesa magnetic drum for main memory, and a punch tape and printer for reading and writing data respectively. In both examples, computer buses of one form or another move data between all of these devices.
In most traditional computer architecturesthe CPU and main memory tend to be tightly coupled. A microprocessor conventionally is a single chip which has a number of electrical connections on its pins that can be used to select an "address" in the main memory and another set of pins to read and write the data stored at that location.
In most cases, the CPU and memory share signalling characteristics and operate in synchrony. The bus connecting the CPU and memory is one of the defining characteristics of the system, and often referred to simply as the system bus.
It is possible to allow peripherals to communicate with memory in the same fashion, attaching adaptors in the form of expansion cards directly to the system bus. This is commonly accomplished through some sort of standardized electrical connector, several of these forming the expansion bus or local bus.
However, as the performance differences between the CPU and peripherals varies widely, some solution is generally needed to ensure that peripherals do not slow overall system performance.
Many CPUs feature a second set of pins similar to those for communicating with memory, but able to operate at very different speeds and using different protocols. Others use smart controllers to place the data directly in memory, a concept known as direct memory access.
Most modern systems combine both solutions, where appropriate. As the number of potential peripherals grew, using an expansion card for every peripheral became increasingly untenable. This has led to the introduction of bus systems designed specifically to support multiple peripherals.
Common examples are the SATA ports in modern computers, which allow a number of hard drives to be connected without the need for a card. However, these high-performance systems are generally too expensive to implement in low-end devices, like a mouse.
This has led to the parallel development of a number of low-performance bus systems for these solutions, the most common example being the standardized Universal Serial Bus USB.
All such examples may be referred to as peripheral busesalthough this terminology is not universal.
In modern systems the performance difference between the CPU and main memory has grown so great that increasing amounts of high-speed memory is built directly into the CPU, known as a cache. In such systems, CPUs communicate using high-performance buses that operate at speeds much greater than memory, and communicate with memory using protocols similar to those used solely for peripherals in the past.
These system buses are also used to communicate with most or all other peripherals, through adaptors, which in turn talk to other peripherals and controllers. Such systems are architecturally more similar to multicomputerscommunicating over a bus rather than a network.
In these cases, expansion buses are entirely separate and no longer share any architecture with their host CPU and may in fact support many different CPUs, as is the case with PCI.
What would have formerly been a system bus is now often known as a front-side bus. Given these changes, the classical terms "system", "expansion" and "peripheral" no longer have the same connotations. Other common categorization systems are based on the bus's primary role, connecting devices internally or externally, PCI vs.
However, many common modern bus systems can be used for both; SATA and the associated eSATA are one example of a system that would formerly be described as internal, while certain automotive applications use the primarily external IEEE in a fashion more similar to a system bus.
Internal buses[ edit ] The internal bus, also known as internal data bus, memory bus, system bus or Front-Side-Bus, connects all the internal components of a computer, such as CPU and memory, to the motherboard. Internal data buses are also referred to as a local bus, because they are intended to connect to local devices.
This bus is typically rather quick and is independent of the rest of the computer operations. External buses[ edit ] The external bus, or expansion busis made up of the electronic pathways that connect the different external devices, such as printer etc.
Implementation details[ edit ] Buses can be parallel buseswhich carry data words in parallel on multiple wires, or serial buseswhich carry data in bit-serial form.
As data rates increase, the problems of timing skewpower consumption, electromagnetic interference and crosstalk across parallel buses become more and more difficult to circumvent. One partial solution to this problem has been to double pump the bus.
Often, a serial bus can be operated at higher overall data rates than a parallel bus, despite having fewer electrical connections, because a serial bus inherently has no timing skew or crosstalk. Multidrop connections do not work well for fast serial buses, so most modern serial buses use daisy-chain or hub designs.
Network connections such as Ethernet are not generally regarded as buses, although the difference is largely conceptual rather than practical.Mr. Dan Burleson. ARMY SERIAL NUMBER TRACKING (ARSNT) MAJOR ITEMS. U.S. Army Materiel Command. PARTICIPATION IN SN TRACKING (COORDINATION/SUPPORT).
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In the past several decades there has been a revolution in computing and communications, and all indications are that technological development and use of information and facts technology will. The official DVD FAQ (Frequently Asked Questions about DVD) of the Internet DVD newsgroups.
The most comprehensive source of DVD technical information in the galaxy. By Jim Taylor. In computer architecture, a bus (a contraction of the Latin omnibus) is a communication system that transfers data between components inside a computer, or between timberdesignmag.com expression covers all related hardware components (wire, optical fiber, etc.) and software, including communication protocols.
Early computer buses were parallel electrical wires with multiple hardware connections. View and Download IBM Enterprise Storage Server E10 introduction and planning manual online. Enterprise Storage Server E10 Server pdf manual download.
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