Hardware Reference
In-Depth Information
cult to obtain and upgrades are generally not available. When you consider that the power
supply is one of the most failure-prone components, purchasing systems that use propri-
etary designs can be a significant liability in the future. If you need a replacement for a
proprietary form factor supply, one of the best sources is
ATXPowerSupplies.com
. They
maintain replacement models that cover a huge number of both proprietary and industry
standard designs.
See
“
Motherboard Form Factors
,”
p.
143
(
Chapter 4
, “
Motherboards and Buses
”
).
Modern Form Factors
The power supply form factors detailed in the following sections are the standards used
in current systems. ATX is far and away the most common of these, but if you work on a
variety of PC types, you are likely to encounter the other types listed here.
ATX/ATX12V
In 1995, Intel saw that the existing power supply designs were literally running out of
power. The problem was that the existing standards used two connectors with a total of
only 12 pins providing power to the motherboard. In addition, the connectors used were
difficult to properly key, and plugging them in improperly resulted in short-circuiting and
damage to both the motherboard and the power supply. To solve these problems, in 1995
Intel took the existing popular LPX (PS/2) design and simply changed the internal cir-
cuitry and connectors (while leaving the mechanical shape the same), giving birth to the
ATX power supply form factor (see
Figure 18.1
)
.
Figure 18.1
ATX12V 2.x form factor power supply with 24-pin main, 4-pin +12V, and optional PCI Ex-
press Graphics connectors.
