Hardware Reference
In-Depth Information
Figure 18.1. ATX12V 2.x form factor power supply with 24-pin main, 4-pin +12V, and optional
PCI Express Graphics connectors.
Intel released the ATX specification in 1995, and in 1996, it started to become increasingly popular
in Pentium and Pentium Pro-based PCs, capturing 18% of the market within the first year. Since
1996, ATX variants have become both the dominant motherboard and power supply form factors,
replacing the previously popular Baby-AT/LPX designs. ATX12V power supplies are also used with
newer motherboard form factors such as BTX, ensuring that ATX and its derivatives will remain the
most popular power supply form factors for several years to come. The ATX12V specification
defines the physical or mechanical form as well as the electrical connectors for the power supply.
From 1995 through early 2000, the ATX power supply form factor was defined as part of the ATX
motherboard specification. However, in February 2000, Intel took the power supply specification out
of the then-current ATX 2.03 motherboard/chassis specification and created the ATX/ATX12V
power supply specification 1.0, adding an optional 4-pin +12V connector at the same time. (Those
