Editing Serial communication (section)

==Serial versus parallel==
The communication links, across which computers (or parts of computers) talk to one another, may be either serial or parallel. A parallel link transmits several streams of data simultaneously along multiple channels (e.g., wires, printed circuit tracks, or optical fibers); whereas, a serial link transmits only a single stream of data. The rationale for parallel communication was the added benefit of having [[Direct Memory Access]] to the 8-bit or 16-bit registry addresses at a time where mapping direct data lanes was more convenient and faster than synchronizing data serially.{{cn|date=May 2024}}

Although a serial link may seem inferior to a parallel one, since it can transmit less data per clock cycle, it is often the case that serial links can be clocked considerably faster than parallel links in order to achieve a higher data rate. Several factors allow serial to be clocked at a higher rate:
*[[Clock skew]] between different channels is not an issue (for unclocked [[asynchronous serial communication]] links). This can be caused by mismatched wire or conductor lengths.<ref name="cse378-lecture-24">{{cite web |url=https://courses.cs.washington.edu/courses/cse378/11wi/lectures/lec24.pdf |title=Lecture 24 |work=CSE378: Machine Organization & Assembly Language}}</ref><ref>{{cite book | url=https://books.google.com/books?id=BxptEAAAQBAJ | title=Modern Computer Architecture and Organization: Learn x86, ARM, and RISC-V architectures and the design of smartphones, PCS, and cloud servers | isbn=978-1-80323-823-4 | last1=Ledin | first1=Jim | last2=Farley | first2=Dave | date=4 May 2022 | publisher=Packt Publishing }}</ref>
*A serial connection requires fewer interconnecting cables (e.g., wires/fibers) and hence occupies less space. The extra space allows for better isolation of the channel from its surroundings.
*[[Crosstalk]] is less of an issue, because there are fewer conductors in proximity.<ref name="cse378-lecture-24" />
*Budgets for power use, power dissipation, cable cost, component cost, IC die area, PC board area, ESD protection, etc. can be focused on a single link.

The transition from parallel to serial buses was allowed by [[Moore's law]] which allowed for the incorporation of SerDes in integrated circuits.<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>
An electrical serial link only requires a pair of wires, whereas a parallel link requires several. Thus serial links can save on costs (also known as the [[Bill of Materials]]). [[Differential signalling]] uses length-matched wires or conductors and are used in high speed serial links.<ref>{{cite book | url=https://books.google.com/books?id=BxptEAAAQBAJ | title=Modern Computer Architecture and Organization: Learn x86, ARM, and RISC-V architectures and the design of smartphones, PCS, and cloud servers | isbn=978-1-80323-823-4 | last1=Ledin | first1=Jim | last2=Farley | first2=Dave | date=4 May 2022 | publisher=Packt Publishing }}</ref> Length-matching is easier to perform on serial links as they require fewer conductors.

In many cases, serial is cheaper to implement than parallel. Many [[Integrated circuit|IC]]s have serial interfaces, as opposed to parallel ones, so that they have fewer pins and are therefore less expensive.