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Guy Harris (talk | contribs) →Implementation details: Spell out "serializer/deserializers", for the benefit of those unfamiliar with "SerDes" but perhaps familiar with the notions of serializing and deserializing. |
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Buses can be [[parallel bus]]es, which carry [[data word]]s in parallel on multiple wires, or [[serial bus]]es, which carry data in bit-serial form. The addition of extra power and control connections, [[differential signaling|differential driver]]s, and data connections in each direction usually means that most serial buses have more conductors than the minimum of one used in [[1-Wire]] and [[UNI/O]]. As data rates increase, the problems of [[timing skew]], power 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. [[USB]], [[FireWire]], and [[Serial ATA]] are examples of this. [[Multidrop]] connections do not work well for fast serial buses, so most modern serial buses use [[Daisy chain (information technology)#Computer hardware|daisy-chain]] or hub designs.
The transition from parallel to serial buses was allowed by [[Moore's law]] which allowed for the incorporation of [[SerDes|serializer/deserializers]] in integrated circuits which are used in computers.<ref>{{cite book | url=https://books.google.com/books?id=aUCgNOpyUbgC&dq=parallel++serial++serdes+moore%27s+law&pg=PA275 | isbn=978-1-4020-7496-7 | title=The Boundary — Scan Handbook | date=30 June 2003 | publisher=Springer }}</ref>
[[computer network|Network]] connections such as [[Ethernet]] are not generally regarded as buses, although the difference is largely conceptual rather than practical. An attribute generally used to characterize a bus is that power is provided by the bus for the connected hardware. This emphasizes the [[busbar]] origins of bus architecture as supplying switched or distributed power. This excludes, as buses, schemes such as serial [[RS-232]], parallel [[Centronics]], [[IEEE 1284]] interfaces and Ethernet, since these devices also needed separate power supplies. [[Universal Serial Bus]] devices may use the bus supplied power, but often use a separate power source. This distinction is exemplified by a [[Plain old telephone service|telephone]] system with a connected [[modem]], where the [[RJ11]] connection and associated modulated signalling scheme is not considered a bus, and is analogous to an [[Ethernet]] connection. A phone line connection scheme is not considered to be a bus with respect to signals, but the [[telephone exchange|Central Office]] uses buses with [[cross-bar switch]]es for connections between phones.
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