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{{Short description|Group of electrical connectors specifically aligned}} | {{Short description|Group of electrical connectors specifically aligned}} | ||
{{Use dmy dates|date= | {{More citations needed|date=May 2026}} | ||
[[ | {{Use dmy dates|date=May 2026}} | ||
[[File:PICMG-Backplane-Details.jpg|thumb|Major components on a PICMG 1.3 active backplane]] | |||
[[File:PDP-8I-backplane.jpg|thumb|Wire-wrapped backplane from a 1960s [[PDP-8]] minicomputer]] | [[File:PDP-8I-backplane.jpg|thumb|Wire-wrapped backplane from a 1960s [[PDP-8]] minicomputer]] | ||
A '''backplane''' or '''backplane system''' is a group of [[electrical connector]]s in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a [[computer bus]]. It is used to connect several printed circuit boards together to make up a complete [[computer system]]. Backplanes commonly use a [[printed circuit board]], but [[Wire wrap|wire-wrapped]] backplanes have also been used in [[minicomputer]]s and high-reliability applications. | A '''backplane''' or '''backplane system''' is a group of [[electrical connector]]s in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a [[computer bus]]. It is used to connect several printed circuit boards together to make up a complete [[computer system]]. Backplanes commonly use a [[printed circuit board]], but [[Wire wrap|wire-wrapped]] backplanes have also been used in [[minicomputer]]s and high-reliability applications. | ||
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Early microcomputer systems like the [[Altair 8800]] used a backplane for the processor and [[expansion card]]s. | Early microcomputer systems like the [[Altair 8800]] used a backplane for the processor and [[expansion card]]s. | ||
Backplanes are normally used in preference to cables because of their greater [[Reliability engineering|reliability]]. In a cabled system, the cables need to be flexed every time that a card is added or removed from the system; this flexing eventually causes mechanical failures. A backplane does not suffer from this problem, so its service life is limited only by the longevity of its connectors. For example, [[DIN 41612]] connectors (used in the [[VMEbus]] system) have three durability grades built to withstand (respectively) 50, 400 and 500 insertions and removals, or "mating cycles". To transmit information, Serial Back-Plane technology uses a [[low-voltage differential signaling]] transmission method for sending information.<ref>{{cite | Backplanes are normally used in preference to cables because of their greater [[Reliability engineering|reliability]]. In a cabled system, the cables need to be flexed every time that a card is added or removed from the system; this flexing eventually causes mechanical failures. A backplane does not suffer from this problem, so its service life is limited only by the longevity of its connectors. For example, [[DIN 41612]] connectors (used in the [[VMEbus]] system) have three durability grades built to withstand (respectively) 50, 400 and 500 insertions and removals, or "mating cycles". To transmit information, Serial Back-Plane technology uses a [[low-voltage differential signaling]] transmission method for sending information.<ref>{{cite conference |last=Varnavas |first=Kosta |date=2005 |title=Serial Back-Plane Technologies in Advanced Avionics Architectures |url=https://zenodo.org/record/1267253 |conference=24th Digital Avionics Systems Conference |volume=2 |doi=10.1109/DASC.2005.1563416 |isbn=978-0-7803-9307-3 |s2cid=8974309 }}</ref> | ||
In addition, there are bus expansion cables which will extend a computer bus to an external backplane, usually located in an enclosure, to provide more or different slots than the host computer provides. These cable sets have a transmitter board located in the computer, an expansion board in the remote backplane, and a cable between the two. | In addition, there are bus expansion cables which will extend a computer bus to an external backplane, usually located in an enclosure, to provide more or different slots than the host computer provides. These cable sets have a transmitter board located in the computer, an expansion board in the remote backplane, and a cable between the two. | ||
==Active | ==Active versus passive backplanes== | ||
[[ | [[File:ISA-Backplane.jpg|thumb|ISA passive backplane showing connectors and parallel signal traces on back side. Only components are connectors, capacitors, resistors and voltage indicator LEDs.]] | ||
Backplanes have grown in complexity from the simple [[Industry Standard Architecture]] (ISA) (used in the original [[IBM PC]]) or [[S-100 bus|S-100]] style where all the connectors were connected to a common bus. Due to limitations inherent in the [[Peripheral Component Interconnect]] (PCI) specification for driving slots, backplanes are now offered as '''passive''' and '''active'''. | Backplanes have grown in complexity from the simple [[Industry Standard Architecture]] (ISA) (used in the original [[IBM PC]]) or [[S-100 bus|S-100]] style where all the connectors were connected to a common bus. Due to limitations inherent in the [[Peripheral Component Interconnect]] (PCI) specification for driving slots, backplanes are now offered as '''passive''' and '''active'''. | ||
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The distinction between the two isn't always clear, but may become an important issue if a whole system is expected to not have a [[single point of failure]] (SPOF) . Common myth around passive backplane, even if it ''is'' single, is not usually considered a SPOF. Active back-planes are even more complicated and thus have a non-zero risk of malfunction. However one situation that can cause disruption both in the case of Active and Passive Back-planes is while performing maintenance activities i.e. while swapping boards there is always a possibility of damaging the Pins/Connectors on the Back-plane, this may cause full outage for the system as all boards mounted on the back-plane should be removed in order to fix the system. Therefore, we are seeing newer architectures where systems use high speed redundant connectivity to interconnect system boards point to point with No Single Point of Failure anywhere in the system. | The distinction between the two isn't always clear, but may become an important issue if a whole system is expected to not have a [[single point of failure]] (SPOF) . Common myth around passive backplane, even if it ''is'' single, is not usually considered a SPOF. Active back-planes are even more complicated and thus have a non-zero risk of malfunction. However one situation that can cause disruption both in the case of Active and Passive Back-planes is while performing maintenance activities i.e. while swapping boards there is always a possibility of damaging the Pins/Connectors on the Back-plane, this may cause full outage for the system as all boards mounted on the back-plane should be removed in order to fix the system. Therefore, we are seeing newer architectures where systems use high speed redundant connectivity to interconnect system boards point to point with No Single Point of Failure anywhere in the system. | ||
==Backplanes | ==Backplanes versus motherboards== | ||
When a backplane is used with a plug-in [[single-board computer]] (SBC) or | When a backplane is used with a plug-in [[single-board computer]] (SBC) or system host board (SHB), the combination provides the same functionality as a [[motherboard]], providing processing power, memory, I/O and slots for plug-in cards. While there are a few motherboards that offer more than eight slots, that is the traditional limit. In addition, as technology progresses, the availability and number of a particular slot type may be limited in terms of what is currently offered by motherboard manufacturers. | ||
However, backplane architecture is somewhat unrelated to the SBC technology plugged into it. There are some limitations to what can be constructed, in that the SBC chip set and processor have to provide the capability of supporting the slot types. In addition, virtually an unlimited number of slots can be provided with 20, including the SBC slot, as a practical though not an absolute limit. Thus, a PICMG backplane can provide any number and any mix of ISA, PCI, PCI-X, and PCI-e slots, limited only by the ability of the SBC to interface to and drive those slots. For example, an SBC with the latest i7 processor could interface with a backplane providing up to 19 ISA slots to drive legacy I/O cards. | However, backplane architecture is somewhat unrelated to the SBC technology plugged into it. There are some limitations to what can be constructed, in that the SBC chip set and processor have to provide the capability of supporting the slot types. In addition, virtually an unlimited number of slots can be provided with 20, including the SBC slot, as a practical though not an absolute limit. Thus, a PICMG backplane can provide any number and any mix of ISA, PCI, PCI-X, and PCI-e slots, limited only by the ability of the SBC to interface to and drive those slots. For example, an SBC with the latest i7 processor could interface with a backplane providing up to 19 ISA slots to drive legacy I/O cards. | ||
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A "virtual midplane" is an imaginary plane between vertical cards on one side that directly connect to horizontal boards on the other side; the card-slot aligners of the card cage and self-aligning connectors on the cards hold the cards in position.<ref> | A "virtual midplane" is an imaginary plane between vertical cards on one side that directly connect to horizontal boards on the other side; the card-slot aligners of the card cage and self-aligning connectors on the cards hold the cards in position.<ref> | ||
Michael Fowler. | Michael Fowler. | ||
[ | [https://electronicdesign.com/boards/virtual-midplane-realizes-ultrafast-card-interconnects "Virtual Midplane Realizes Ultrafast Card Interconnects"]. | ||
Electronic Design. | Electronic Design. | ||
2002. | 2002. | ||
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</ref> | </ref> | ||
== | ==Backplanes in storage<span class="anchor" id="STORAGE"></span><span class="anchor" id="Backplanes in storage"></span>== | ||
Servers commonly have a backplane to attach hot swappable hard disk drives and solid state drives; backplane pins pass directly into hard drive sockets without cables. They may have single connector to connect one [[disk array controller]] or multiple connectors that can be connected to one or more controllers in arbitrary way. Backplanes are commonly found in [[disk enclosure]]s, [[disk array]]s, and [[Server (computing)|server]]s. | Servers commonly have a backplane to attach hot swappable hard disk drives and solid state drives; backplane pins pass directly into hard drive sockets without cables. They may have single connector to connect one [[disk array controller]] or multiple connectors that can be connected to one or more controllers in arbitrary way. Backplanes are commonly found in [[disk enclosure]]s, [[disk array]]s, and [[Server (computing)|server]]s. | ||
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==Platforms== | ==Platforms== | ||
===PICMG=== | ===PICMG=== | ||
[[ | {{Main|PICMG}} | ||
[[File:SBC-Backplane.jpg|thumb|A [[single-board computer]] installed into a [[#Active versus passive backplanes|passive]] backplane]] | |||
A single-board computer meeting the PICMG 1.3 specification and compatible with a PICMG 1.3 backplane is referred to as a ''system host board''. | |||
A single-board computer meeting the PICMG 1.3 specification and compatible with a PICMG 1.3 backplane is referred to as a | |||
In the Intel | In the Intel single-board computer ecosystem, [[PICMG]] provides standards for the backplane interface: [[PICMG 1.0]], 1.1 and 1.2<ref>{{cite web|url=http://www.picmgeu.org/specs/available_specifications.htm |title=PICMG 1.0, 1.1 and 1.2 |publisher=Picmgeu.org |access-date=20 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120626143521/http://www.picmgeu.org/specs/available_specifications.htm |archive-date=26 June 2012 }}</ref> provide ISA and PCI support, with 1.2 adding PCIX support. PICMG 1.3 provides PCI-Express support.<ref>{{cite web|url=http://www.picmgeu.org/specs/available_specifications.htm |title=PICMG 1.3 |publisher=Picmgeu.org |access-date=20 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120626143521/http://www.picmgeu.org/specs/available_specifications.htm |archive-date=26 June 2012 }}</ref><ref>{{cite web|url=http://www.picmg.org/v2internal/SHB_Express.htm |title=PICMG 1.3 SHB Express Resources |publisher=Picmg.org |access-date=20 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121130222348/http://www.picmg.org/v2internal/SHB_Express.htm |archive-date=30 November 2012 }}</ref> | ||
[[PICMG 1.0]], 1.1 and 1.2<ref>{{cite web|url=http://www.picmgeu.org/specs/available_specifications.htm |title=PICMG 1.0, 1.1 and 1.2 |publisher=Picmgeu.org |access-date=20 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120626143521/http://www.picmgeu.org/specs/available_specifications.htm |archive-date=26 June 2012 }}</ref> provide ISA and PCI support, with 1.2 adding PCIX support. | |||
PICMG 1.3<ref>{{cite web|url=http://www.picmgeu.org/specs/available_specifications.htm |title=PICMG 1.3 |publisher=Picmgeu.org |access-date=20 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120626143521/http://www.picmgeu.org/specs/available_specifications.htm |archive-date=26 June 2012 }}</ref><ref>{{cite web|url=http://www.picmg.org/v2internal/SHB_Express.htm |title=PICMG 1.3 SHB Express Resources |publisher=Picmg.org |access-date=20 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121130222348/http://www.picmg.org/v2internal/SHB_Express.htm |archive-date=30 November 2012 }}</ref> | |||
==See also== | ==See also== | ||
* | * {{Annotated link|Daughterboard}} | ||
* | * {{Annotated link|Eurocard (printed circuit board)|Eurocard}} | ||
* | * {{Annotated link|M-Module}} | ||
* {{Annotated link|SS-50 Bus}} | |||
* | * {{Annotated link|STD Bus}} | ||
* | * {{Annotated link|STEbus}} | ||
* | * {{Annotated link|Switched fabric}} | ||
* | * {{Annotated link|VXI}} | ||
* | |||
==References== | ==References== | ||
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==Further reading== | ==Further reading== | ||
* {{cite journal |last1=Karanassios |first1=V. |last2=Horlick |first2=G. |title=Backplane bus structures and systems |journal=Talanta | {{Commons category|Backplanes}} | ||
* {{cite journal |last1=Karanassios |first1=V. |last2=Horlick |first2=G. |title=Smart backplanes—I: The apple II |journal=Talanta | * {{cite journal |last1=Karanassios |first1=V. |last2=Horlick |first2=G. |date=August 1985 |title=Backplane bus structures and systems |journal=Talanta |volume=32 |issue=8 |pages=583–599 |doi=10.1016/0039-9140(85)80155-7 |pmid=18963977 |oclc=269384772 }} | ||
* {{cite journal |last1=Karanassios |first1=V. |last2=Horlick |first2=G. |title=Smart backplanes—II: The IBM PC |journal=Talanta | * {{cite journal |last1=Karanassios |first1=V. |last2=Horlick |first2=G. |date=August 1985 |title=Smart backplanes—I: The apple II |journal=Talanta |volume=32 |issue=8 |pages=601–614 |doi=10.1016/0039-9140(85)80156-9 |pmid=18963978 |oclc=4928218486 }} | ||
* {{cite journal |last1=Karanassios |first1=V. |last2=Horlick |first2=G. |date=August 1985 |title=Smart backplanes—II: The IBM PC |journal=Talanta |volume=32 |issue=8 |pages=615–631 |doi=10.1016/0039-9140(85)80157-0 |pmid=18963979 |oclc=269384774 }} | |||
[[Category:Computer buses]] | [[Category:Computer buses]] | ||