Motherboards and Buses - Upgrading and Repairing PCs - page 157

Although NLX is a standard form factor—just as the ATX family is—most NLX products were sold
as part of complete systems aimed at the corporate market. Few aftermarket motherboards have been
developed in this form factor. The microATX and FlexATX form factors have superseded NLX in the
markets formerly dominated by LPX.
WTX
WTX was a board and system form factor developed for the mid-range workstation market; however,
most vendors making workstations and servers have used the ATX form factor. WTX went beyond
ATX and defined the size and shape of the board and the interface between the board and chassis, as
well as required chassis features.
WTX was released in September 1998 (1.0) and updated in February 1999 (1.1). Since then,
however, WTX has been officially discontinued, and there will be no further updates.
BTX
Balanced Technology Extended (BTX) is a motherboard form factor specification that Intel released
in September 2003, with 1.0a and 1.0b updates released in February 2004 and July 2005,
respectively. BTX was designed to address the ever-increasing component power and cooling
requirements, as well as enabling improved circuit routing and more flexible chassis designs.
However, the recent trend toward more power efficient dual-core processor designs has slowed the
need for the benefits inherent in the BTX standard, which has in turn slowed the adoption of BTX,
causing Intel to announce in late 2006 that it was abandoning future BTX development. BTX was
popular in many mass-produced retail-branded PCs sold between 2005 and 2007, such as those by
Dell, Gateway, and others. Since then the BTX form factor has largely been abandoned.
BTX is not backward-compatible with ATX or other designs. A full-size BTX board is 17% larger
than ATX, allowing room for more integrated components onboard. The I/O connectors, slots, and
mounting holes are in different locations than with ATX, requiring new chassis designs. However, the
power supply interface connectors are the same as in the latest ATX12V specifications, and newer
ATX, TFX, SFX, CFX, and LFX power supplies can be used. The latter two power supply form
factors were specifically created to support compact and low-profile BTX systems.
The primary advantages to BTX include optimized inline component layout and routing, optimized
airflow path, a support and retention module (SRM) for heavy heatsinks, scalable board dimensions,
low-profile options, and flexible power supply designs with connector types that are compatible with
ATX designs.
BTX includes three definitions of motherboard size, as shown in Table 4.1 .
Table 4.1. BTX Motherboard Form Factors
Each board has the same basic screw hole and connector placement requirements. So, if you have a
case that fits a full-size BTX board, you can also mount a microBTX or picoBTX board in that same