Power Supplies - Upgrading and Repairing PCs - page 1092

nectors used as well as the pinouts of the individual wires and terminals. Unfortunately,
just as with the mechanical form factors, some PC manufacturers use power supplies with
custom connectors or, worse yet, use standard connector types but with modified (incom-
patible)pinouts(meaningthesignalsandvoltagesarerearrangedfromstandardspecifica-
tions). Plugging a power supply with an incompatible pinout into a motherboard that uses
a standard pinout (or vice versa) usually results in the destruction of either the board or
the power supply—or both.
Just as I insist on industry-standard mechanical form factors in my systems, I also want to
ensure that they use industry-standard connectors and pinouts. By only purchasing com-
ponentsthatconformtoindustrystandards, Icanensurethegreatest flexibility andlowest
cost for future upgrades and repairs.
Two main sets of motherboard power connectors have been used over the years: what I
would call AT/LPX type and the ATX type. Each of these has minor variations; for ex-
ample, the ATX type has evolved over the years, with new connectors coming (and some
going) and modifications to existing connectors. This section details the motherboard
power connectors used by various types of industry-standard (and some not-so-standard)
power supplies.
AT/LPX Power Supply Connectors
Industry-standard PC, XT, AT, Baby-AT, and LPX motherboards use the same type of
main power supply connectors. AT/LPX power supplies feature two main power connect-
ors (P8 and P9), each with six pins that attach the power supply to the motherboard. The
terminals used in these connectors are rated to handle up to 5 amps at up to 250V (even
though the maximum used in a PC is +12V). These two connectors are shown in Figure
18.18 .
Figure 18.18 AT/LPX main P8/P9 (also called P1/P2) power connectors, side and terminal end view.