Power Supplies - Upgrading and Repairing PCs - page 859

modern power supply form factors are all about. The bottom line is that it is up to you to ensure that
the power supply you purchase not only plugs in to your motherboard, but also fits into the chassis or
case you plan to use.
Tables 18.2 and 18.3 show the industry-standard power supply form factors, their connector types,
and the motherboard form factors with which they are usually associated.
Table 18.2. Modern Industry-Standard Power Supply Form Factors
Table 18.3. Obsolete Industry Standard Power Supply Form Factors
You may encounter power supplies using obsolete form factors if you work on PCs built in the 1980s
through the mid-1990s. I cover them in more detail in the 18 th and earlier editions of this topic.
Each of these power supply form factors is, or has been, available in numerous configurations and
power output levels. The obsolete LPX form factor supply originated in the IBM PS/2 Model 30 in
April 1987 and was the standard used on most systems from the late 1980s to mid-1996, when the
ATX form factor started to gain in popularity. Since then, ATX and the many variants based on ATX
have become by far the dominant form factors for power supplies. It is interesting to note that IBM's
legacy lives on even now because ATX, PS3, and EPS are all based on the LPX (PS/2) physical form
factor. Any power supply that does not conform to one of these standards is considered proprietary .
In general, avoid systems that use proprietary power supply designs because replacements are
difficult 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 proprietary 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