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Additional Power Connectors: Peripheral, Floppy, And SATA

Power Supply 101: A Reference Of Specifications
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Besides the motherboard power connectors, all power supplies include a variety of additional power connectors, mainly used for internally mounted drives but usable by other components, such as graphics cards. Most of these connectors are industry-standard types required by the various power supply form factor specifications. This section discusses the various types of additional device power connectors you’re likely to find in your PC.

Peripheral Power Connectors

Perhaps the most common additional power connector seen on virtually all power supplies is the peripheral power connector, also called the disk drive power connector. What we know as the peripheral power connector was originally created by AMP as part of the commercial MATE-N-LOK series, although since it is also manufactured and sold by Molex, it is often incorrectly called a Molex connector.

To determine the location of pin one, carefully look at the connector. It is usually embossed in the plastic connector body; however, it is often tiny and difficult to read. Fortunately, these connectors are keyed and therefore difficult to insert incorrectly. The following image shows the keying with respect to pin numbers on the larger drive power connector.

A peripheral power connector.A peripheral power connector.

This is the one connector type that has been on all PC power supplies from the original IBM PC to the latest systems built today. It is most commonly known as a disk drive connector, but it is also used in some systems to provide additional power to the motherboard, video card, cooling fans, or just about anything that can use +5 V or +12 V power.

A peripheral power connector is a four-pin connector with round terminals spaced 0.200 inches apart, rated to carry up to 11 amps per pin. Because there is one +12 V pin and one +5 V pin (the other two are grounds), the maximum power-handling capability of the peripheral connector is 187 watts. The plug is 0.830 inches wide, making it suitable for larger drives and devices.

The next table shows the peripheral power connector pinout and wire colors.

Peripheral Power Connector Pinout (Large Drive Power Connector)
Pin
Signal
Color
Pin
Signal
Color
1
+12 VYellow3
GndBlack
2
GndBlack4
+5 VRed


Floppy Power Connectors

When 3.5-inch floppy drives were first being integrated into PCs in the mid-1980s, it was clear that a smaller power connector was necessary. The answer came in what is now known as the floppy power connector, which was created by AMP as part of the economy interconnection (EI) series. These connectors are now used on all types of smaller drives and devices and feature the same +12 V, +5 V, and ground pins as the larger peripheral power connector. The floppy power connector has four pins spaced 2.5 mm (0.098 inches) apart, which makes the entire connector about half the overall width as the larger peripheral power connector. The pins are rated for only two amps each, giving a maximum power-handling capability of 34 watts.

This table shows the pinouts for the smaller floppy drive power connector.

Pinout for the 3.5-Inch Floppy Power Connector (Small Drive Power Connector)
Pin
Signal
Color
Pin
Signal
Color
1
+5 VRed3
GndBlack
2
GndBlack4
+12 VYellow


The peripheral and floppy power connectors are universal with regard to pin configuration and even wire color. Here we see the peripheral and floppy power connectors.

Peripheral and floppy power connectors.Peripheral and floppy power connectors.

The pin numbering and voltage designations are reversed on the floppy power connector. Be careful if you are making or using an adapter cable from one type of connector to another. Reversing the red and yellow wires fries the drive or device you plug into.

Early power supplies featured only two peripheral power connectors, whereas later power supplies featured four or more of the larger peripheral (disk drive) connectors and one or two of the smaller floppy power connectors. Depending on their power ratings and intended uses, some supplies have as many as eight or more peripheral or floppy power connectors.

If you are adding drives and need additional power connectors, Y splitter cables as well as peripheral-to-floppy power connector adapters are available from many electronics supply houses (including RadioShack). These cables can adapt a single power connector to service two drives or enable you to convert the large peripheral power connector to a smaller floppy drive power connector. If you are using several Y-adapters, be sure that your total power supply output is capable of supplying the additional power and that you don’t draw more power than a single connector can handle.

Serial ATA Power Connectors

If you want to add Serial ATA drives to an existing system, you will need a newer power supply that includes a Serial ATA (SATA) power connector. The SATA power connector is a special 15-pin connector fed by only five wires, meaning three pins are connected directly to each wire. The overall width is about the same as the peripheral power connector, but the SATA connector is significantly thinner. All the most recent power supply form factor specifications include SATA power connectors as mandatory for systems supporting SATA drives.

A SATA power connector.A SATA power connector.

In the SATA power connector, each wire is connected to three terminal pins, and the wire numbering is not in sync with the terminal numbering, which can be confusing.

If your power supply does not feature SATA power connectors, you can use an adapter to convert a standard peripheral power connector to a SATA power connector. However, such adapters do not include the +3.3 V power. Fortunately, though, this is not a problem for most applications because most drives do not require +3.3 V and use only +12 V and +5 V instead.

A peripheral-to-SATA power connector adapter.A peripheral-to-SATA power connector adapter.

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