Although Dell is one of the largest computer manufacturers in the world, the company outsources the production of motherboards for its systems to companies such as Asus, Foxconn, Intel and many others. On many Dell motherboards, you'll usually find at least one Aux_Pwr port, or an auxiliary power connector. Depending on which Dell motherboard in the computer you own, the Aux_Pwr ports may receive power from the power supply for the motherboard and processor or provide needed current to other accessory or cooling devices.
Aux Ports for Fans
With most Dell motherboards, the company designed Aux_Pwr ports for use with CPU or chassis fans. CPU fans cool the processor, while chassis fans are usually 80 mm or 120 mm fans that cool the entire case or bays that house hard drives and optical drives. These types of auxiliary ports usually have three small pins, as most fans that connect to motherboard Aux_Pwr ports have connectors with three female sockets. In a few rare cases, the Aux_Pwr ports on Dell motherboards have 4-pin connectors. However, with models of motherboards that do have auxiliary power ports with four pins, Dell usually includes a fan compatible with them. With the standard 3-pin Aux_Pwr ports, you can use cooling solutions from many aftermarket suppliers that may spin faster and provide better thermal management than stock Dell fans.
Power Supplies and Processors
Although the Aux_Pwr labels on Dell motherboards usually refer to ports used for cooling fans, a few models use the label to refer to the auxiliary power connector for the power supply. Older ATX motherboards usually use single 20-pin or 24-pin power cables for connecting the power supply. Because some modern processors require considerable power, though, many modern Dell motherboards ship with Aux_Pwr ports that enable you to connect separate 12-volt power cables. These cables provide the 12-volt current the motherboard needs to power drives and other peripheral devices rather than drawing it from the main ATX power cable. These types of Aux_Pwr connectors usually have sockets rather than pins. The sockets may consist of a single four, six or eight-socket connector, a combination of two separate four-socket connectors or a “6+2” connection plug. The type of Aux_Pwr socket you find on the Dell motherboard depends on the types of processor the board supports.
In addition to providing power for cooling fans, you can usually use 3-pin Aux_Pwr ports to provide current to other internal devices. For instance, if you have a high-end video card, it may have two or more cooling fans to keep the graphics processing unit from overheating. With some video cards, you must use an auxiliary power connector to provide additional current for the extra cooling fans. If you overclock the processor in your Dell system, water-cooling can help keep the CPU from getting too hot. Many water pumps designed for processors draw power from 3-pin connectors on the motherboard. In many cases, if you connect any type of fan to the 3-pin connector you can usually monitor its status and rotation speed in the system BIOS. Finally, you can also use 3-pin Aux_Pwr ports on Dell motherboards to power custom lighting or LED devices inside the case.
In most cases, you can’t use Aux_Pwr ports on a Dell motherboard that connect to the power supply for any other purpose. Nevertheless, if you have a peripheral or accessory that you want to connect to a 3-pin Aux_Pwr port -- and the power cable for the device doesn't match -- you can purchase an adapter to make the connection. Many computer and electronics stores carry adapter cables that enable you to convert 3-pin Aux_Pwr ports for use with many 4-pin connectors, floppy drive power cables and standard 4--pin Molex peripheral power cables. Therefore, if you don't use the Aux_Pwr port to power a fan, you can connect it to an extra drive or device when the power supply doesn't have enough connector leads.