Form Factors in Motherboard

ATX Motherboard


ATX was developed as an evolution of the Baby-AT form factor and was defined to address ease of use, support for current and future I/O, support for current and future processor technology, and reduced total system cost.


ATX Specification v2.2 Revision 2.2 - [432 KB] Key changes for the ATX Specification Version 2.2 include Main Power Connector changed from 20 pin to 24 pin ( 2 x12) to support PCI-Express* requirements and removed Aux Power Connector Recommendation if using a power supply designed using ATX12V Power Supply Design Guide Rev 2.0 or greater. Also updated the +3.3 V tolerance.


MicroATX Motherboard



The microATX form factor was developed as a natural evolution of the ATX form factor to address new market trends and PC technologies. While offering the same benefits of the ATX form factor specification, the microATX form factor improves upon the previous specification in several key areas. Current trends in the industry indicate that users require a lower-cost solution for their PC needs. Without sacrificing the benefits of ATX, this form factor addresses the cost requirement by reducing the size of the motherboard. The smaller motherboard is made possible by reducing the number of I/O slots supported on the board. The overall effect of these size changes reduces the costs associated with the entire system design. The expected effect of these reductions is to lower the total system cost to the end user.


Through careful designing of a microATX motherboard, an OEM can capitalize on the benefits of a reduction in total system costs. These cost savings come from a reduced-output power supply (see the separate document SFX Power Supply Design Guide), reduced chassis costs, and minimal redesign of existing ATX compliant chassis for backward-compatibility.


microATX benefits also include those found with the current ATX form factor: more I/O space at the rear and reduced emissions from using integrated I/O connectors.


microATX Motherboard Interface Specification v 1.2 Revision 1.2 - [278 KB] Key changes for the microATX Motherboard Interface Specification Version 1.2 include Main Power Connector changed from 20 pin to 24 pin ( 2 x12) to support PCI-Express* requirements

FlexATX Motherboard


FlexATX offers the opportunity for system developers to create many new personal computer designs.

Balanced Technology Extended (BTX) Form Factor


The BTX form factor specification gives developers options to balance thermal management, acoustics, system performance, and size in the system form factors and stylish designs that are desired in today's products. The BTX form factor is a clear break from previous ATX form factor layouts and was developed with emerging technologies such as Serial ATA, USB 2.0, and PCI Express*.

Thermal improvements come primarily from taking advantage of in-line airflow. The BTX defined in-line airflow layout allows many of the main board components (i.e.: processor, chipset, and graphics controller) to utilize the same primary fan airflow, thereby reducing the need for, and noise from, additional system fans. In some cases this also allows fewer and/or less expensive heat sinks to be used when compared to ATX solutions. The system level acoustics are also improved by the reduced air turbulence within the in-line airflow system. The BTX layout supports better component placement for back panel I/O controllers – important as the signal speed of external devices continues to increase. In addition to smaller than microATX system sizes, BTX was designed to scale up to tower size systems using the same core layout by increasing the number of system slots included.




Balanced Technology Extended (BTX) Interface Specification Revision 1.0b - [305 KB]


LPX

White ATX is the most well-known and used form factor, there is also a non-standard proprietary form factor which falls under the name of LPX, and Mini-LPX. The LPX form factor is found in low-profile cases (desktop model as opposed to a tower or mini-tower) with a riser card arrangement for expansion cards where expansion boards run parallel to the motherboard. While this allows for smaller cases it also limits the number of expansion slots available. Most LPX motherboards have sound and video integrated onto the motherboard. While this can make for a low-cost and space saving product they are generally difficult to repair due to a lack of space and overall non-standardization. The LPX form factor is not suited to upgrading and offer poor cooling.


NLX

Boards based on the NLX form factor hit the market in the late 1990's. This "updated LPX" form factor offered support for larger memory modules, tower cases, AGP video support and reduced cable length. In addition, motherboards are easier to remove. The NLX form factor, unlike LPX is an actual standard which means there is more component options for upgrading and repair.
Many systems that were formerly designed to fit the LPX form factor are moving over to NLX. The NLX form factor is well-suited to mass-market retail PCs.