Editing LPX (form factor)

[[File:Dell System 325P Mainboard.jpg|thumb|LPX Mainboard.<br />With introducing the PCI bus, the ISA connector was replaced by a riser card connector, mechanical related to the [[Extended Industry Standard Architecture|EISA]] connector.]]
[[File:PC LPX Riser Card IMG 8614.JPG|thumb|Typical LPX riser card, with connectors for PCI and ISA cards]]
'''LPX''' (short for '''Low Profile eXtension'''), originally developed by [[Western Digital]], was a loosely defined [[motherboard]] format ([[Computer form factor|form factor]]) widely used from 1987 to the late 1990s.<ref name=cram>{{cite book | last=Jones | first=James G. | author2=Craig Landes | author3=Ed Tittel | date=2003 | url=https://books.google.com/books?id=WtE9GN1hhvAC | title=A+ Exam Cram 2: Windows 2000 Directory Services Infrastructure | publisher=Que | pages=25–26 | isbn=9780789728678 | via=Google Books}}</ref><ref name=urp21>{{cite book | last=Mueller | first=Scott | date=2013 | url=https://books.google.com/books?id=Ne3rAQAAQBAJ | title=Upgrading and Repairing PCs | edition=21st | publisher=Que | page=851 | isbn=9780789750006 | via=Google Books}}</ref>

There was never any official LPX specification, but the design normally featured a {{convert|13|xx|9|in|mm|0|abbr=on}} motherboard with the main I/O ports mounted on the back (something that was later adopted by the [[ATX]] form factor), and a [[riser card]] in the center of the motherboard, on which the [[Peripheral Component Interconnect|PCI]] and [[Industry Standard Architecture|ISA]] slots were mounted. This layout was first used on [[IBM]]'s [[IBM PS/2 Model 30|PS/2 Model 30]] personal computer, which Western Digital used as the basis for the creation of LPX.<ref name=urp21 /> Due to the lack of standardized specification, riser cards were seldom compatible from one motherboard design to another, much less one manufacturer to another. The internal [[Power supply unit (computer)|PSU]] connector was of the same type used in the [[AT form factor]].

One of the more successful features to come out of the LPX specification was its use of more compact power supplies, which later became widely used on Baby AT and even full size AT cases.<ref>{{cite web | url=http://www.pcguide.com/ref/power/sup/formLPX-c.html | title=LPX Form Factor | work=PC Guide | accessdate=June 6, 2016}}</ref>  Because LPX form factor power supplies became ubiquitous in most computer cases prior to the ATX standard, it was not unusual for manufacturers to refer to them as "AT" power supplies (or occasionally as "PS/2" power supplies due to its use by the [[IBM PS/2]]), even though the actual AT and Baby AT power supply form factors were larger in size.  The LPX form factor power supply eventually formed the basis for the ATX form factor power supply, which is the same width and height.

The specification was very popular in the early-mid 1990s, and briefly displaced the AT form factor as the most commonly used. However, the release of the [[Pentium II]] in 1997 highlighted the flaws of the format, as a good airflow was important in Pentium II systems, owing to the relatively high heat dispersal requirements of the processor. LPX systems suffered a restricted airflow due to the centrally placed riser cards. The introduction of the [[Accelerated Graphics Port|AGP]] format further complicated matters, as the design not only increased the pin count on riser cards, but it limited most cards to one AGP, one PCI and one ISA slot, which was too restrictive for most users. Some lower-quality LPX boards didn't even feature a real AGP slot, but simply used a physical AGP slot and connected it to the PCI bus. This was seldom noticed however, as many "AGP" graphics cards of the time were in fact PCI cards internally, and did not take advantage of the features offered by AGP.

LPX was phased out around 1998. [[NLX (motherboard form factor)|NLX]] was the intended successor, though many manufacturers chose [[MicroATX]] or proprietary motherboard formats instead.

==References==
{{reflist}}

==External links==
* [http://www.pcguide.com/ref/case/formLPX-c.html LPX form factor] at the PC Guide
{{Computer form factors}}
[[Category:IBM PC compatibles]]
[[Category:Motherboard form factors]]