What is LPX (Low Profile eXtension Form Factor)? Explained

What is LPX (Low Profile eXtension)?

Low Profile eXtension or LPX, refers to a particular form factor of a motherboard. Its typical dimensions are 9 inches wide by 13 inches deep. This makes it suitable for use in slim cases.

This format is technically a modification of the Baby-AT form factor, with a variety of implementations made to its specifications.


  • The LPX motherboards normally have serial, parallel, and PS2 ports like ATX motherboards. The main I/O ports are located at the back of the motherboard.
  • The design allows the expansion slots to be placed on a central riser card, which allows installing them horizontally. This gives it the name Low Profile.
  • This form factor is considered the semi-proprietary design of Western Digital, developed in 1987, due to the lack of exact details of the bus riser card portion and its non-interchangeability between manufacturers.
  • The higher number of ports integrated into the motherboards by some vendors rightfully makes it an all-in-one design.
  • One significant downside of this format is its poor cooling ability due to inadequate air flow, which led to its replacement by the NLX form factor.

Understanding LPX or Low Profile eXtension (Form Factor)

Understanding LPX or Low Profile eXtension (Form Factor)

The LPX form factor was developed in 1987 by Western Digital and was used extensively till the end of the 1990s.

This small form-factor motherboard is quite enough to install most of the necessary components. It comes with a row of connectors, such as:

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There are also a few extra connectors for other different internal ports on a few LPX motherboards, such as SCSI, or Small Computer System Interface, or network adapters.

A few LPX products are considered to have an all-in-one design because a few vendors integrate a higher degree of ports into the motherboard.

The internal connector to the Power Supply Unit of this board is of the same type as that of the AT form factor.

These are more compact, and this specification is widely used in full-size and Baby AT cases.

The good thing about it is that by allowing the use of a riser card, it also allows using expansion cards in the motherboard in parallel and not perpendicular to it, as is usually the case with the AT and ATX motherboards.

This allows mounting ISA or Industry Standard Architecture and PCI or Peripheral Component Interconnect slots on it.

The riser cards, however, are not compatible with one motherboard to another, let alone from one manufacturer to another.

This is due to the lack of standard specifications for the LPX form factor.

In fact, there are a few particular vendors such as HP and IBM that designed systems with a T-shaped riser card.

This allows mounting the cards at a 90° angle to the motherboard and keeping them above it.

Typically, the Low Profile aspect of this motherboard form factor allows it to be used in slim and thin computers instead of a Baby-AT motherboard.

This low profile form factor is also used in desktop computers.

One significant downside of this form factor is that it does not allow for a large number of expansion slots.

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Typically, it is limited to two or three slots.

Often, video adapters are integrated into these particular motherboards along with integrated sound.

This particular feature makes these motherboards cheaper to design but difficult to repair or upgrade.

This is mainly because it is not easy to disable the video card installed on these boards.

These boards are not designed to be used in a home PC because it may be a bit difficult for the builder to work on it because everything on it is pretty cramped.

Apart from that, this is not a standard form factor, which is characterized by a few specific downsides, such as:

  • Poor upgradability
  • Limited expandability and
  • Low cooling ability due to insufficient air flow.

All these factors make it pretty difficult for the home PC builder to use this form factor.

It is mainly due to the difficult arrangement and complex engineering that causes improper air flow and calls for an additional chassis fan.

This is one of the most significant reasons for this form factor to fall out of favor; it was reportedly last used in 1998.

Eventually, this form factor was replaced by its successor, the New Low Profile eXtended form factor.

What is LPX (Low Profile eXtension)

LPX Motherboard Size

Typically, there is no official specification of the size of the LPX form factor.

However, it is usually 13 inches by 9 inches or 330 mm × 229 mm motherboard in depth and width respectively.

However, the lack of a standard specification does not allow replacing a motherboard with another LPX board later.

What is an LPX Power Supply?

The LPX series power supply is the next generation of LP desktop PSUs. These are quite reliable, and depending on the model, there can be a wide range of additional features added into a small form factor design such as electronic filtering, auto ranging, noise shielding, and adjustable output.

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The power supply units of this form factor are used in almost every computer case before the ATX standard.

It is often referred to as “AT power supplies” due to their extensive use, in spite of the fact that the actual form factors of the AT and Baby AT Power Supply Units are larger in size.

Therefore, the LPX power supplies eventually became the foundation of all ATX form factor power supplies, having similar height and width.

These power supplies are also known as PS/2 power supplies because they are used by the IBM PS/2.


The Low Profile eXtended form factor was used extensively in slim computers, desktop computers, and tower cases but was phased out in 1998 by its successor, the NLX, or New Low Profile eXtended form factor.

However, most manufacturers preferred to stick to the Micro ATX instead of NLX form factor.

About Taylor Swift

Taylor SwiftTaylor Swift, a UOPEOPLE graduate is a freelance technology writer with in-depth knowledge about computers. She has an understanding of hardware and technology gained through over 10 years of experience. Follow Her at Linkedin