Hardware Reference
In-Depth Information
This means the total power-handling capacity of this connector is only 251 watts if stand-
ardterminalsarebeingused,whichislowerthanmostsystemsneedtoday.Unfortunately,
drawing more power than this maximum rating through the connector causes it to over-
heat. I'm sure you can appreciate how inadequate this has become today; for example, it
certainly doesn't make sense to manufacture a 400- or 500-watt power supply if the main
power connector can handle only 251 watts without melting! That would be like build-
ing a car that could go 200 mph and then equipping it with tires rated for only 100 mph.
Everything would be fine until you exceeded the tires' rated speed, after which the results
would not be pretty.
This is why the official power supply form factor specifications were updated in March
2005 to include HCS terminals, which have 50% greater power-handling capability than
the standard terminals. Using HCS terminals, the power-handling capability of the 20-pin
mainconnectoraloneincreasesto377watts,whichismorethanmostsystemsneedtorun
the entire system through all the connectors combined.
Six-Pin Auxiliary Power Connector
As motherboards and processors have evolved, the need for power has become greater.
The terminals in the main power connector are rated for 6 amps (A) using standard ter-
minals, which allows for a maximum supply of approximately 250 watts to the mother-
board. Because motherboards with high-speed processors and multiple cards installed
could draw more power than that and power supply manufacturers were building supplies
with 300-watt and higher ratings, melted connectors were becoming more and more com-
mon. The terminals in the main connector overheated under such a load.
To allow for additional power from the supply to the motherboard, Intel modified the
ATX specification to add a second auxiliary power connector for high power-drawing
ATX motherboards and 250-watt or higher rated supplies. The criteria is such that, if the
motherboardcoulddrawmorethan18Aof+3.3Vpowerormorethan24Aof+5Vpower,
