Sign in with
Sign up | Sign in

Additional Power Connectors: Peripheral, Floppy, And SATA

Power Supply 101: A Reference Of Specifications
By

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.

Display all 33 comments.
This thread is closed for comments
  • 5 Hide
    joytech22 , December 14, 2011 4:19 AM
    Quote:
    On the other hand, if you plug into a 240 V outlet and have the switch set for 120 V, you can cause damage.


    Did that when unboxing a computer, must have flipped the small red switch on the supply and boom, at the Windows XP loading bar the PSU exploded. lol.
  • 8 Hide
    cmcghee358 , December 14, 2011 5:05 AM
    Did I miss them covering efficiency and the whole 80 PLUS thing?

    I can't imagine as detailed as it is, omitting something like that...
  • 9 Hide
    cangelini , December 14, 2011 5:59 AM
    cmcghee358Did I miss them covering efficiency and the whole 80 PLUS thing?I can't imagine as detailed as it is, omitting something like that...


    There's still one last part to go!
  • 3 Hide
    cmcghee358 , December 14, 2011 8:55 AM
    But the last part isn't for PSUs. It's just the last part in the series of PC components.
  • 0 Hide
    nikorr , December 14, 2011 9:44 AM
    Thanx ...
  • 0 Hide
    neiroatopelcc , December 14, 2011 10:54 AM
    I wonder how much the power_good signal prevents? is it just the powering of the cpu ?
    I recall once using two power supplies to power a sli board and accidently use a molex from the second supply to power a sli power connector on the motherboard - resulting in fans powering up if you powered the second psu even when the first wasn't on (and if you didn't, the geforces would screech due to lack of power)..... maybe that was just the creative yet rubbish asrock board design, but it certainly didn't need a power_good to power up the fans.

    ps. "Note: If you find that a system consistently fails to boot up properly the first time you turn on the switch, but that it subsequently boots up if you press the reset or Ctrl+Alt+Delete warm boot command, you likely have a problem with the Power_Good timing. You should install a new, higher-quality power supply and see whether that solves the problem."
    Could this explain why I only have 4-6GB memory at post, but 10GB after a quick power off and back on (didn't bother with a reset switch when designing case). Note that 10GB is still 2 short. It used to initialize 10GB - then power off and back on would provide the full amount. Running less than 6GB memory doesn't cause the error.
    Someone said I'd have to reseat the cpu, but maybe it's just that rubbish coolermaster power supply?
  • -2 Hide
    chesteracorgi , December 14, 2011 12:35 PM
    Very informative and interesting. The part about single 12V vs. multiple 12V rails is important reading for system builders who opt for "safer" multiple 12V PSUs. With the current state of design of PSUs anyone planning a sli or Xfire rig is well advised to opt for the single 12V design rather than risk an imbalanced PSU that overvolts a component.
  • 1 Hide
    JohnnyLucky , December 14, 2011 1:06 PM
    Great article. It's not just for beginners.
  • 1 Hide
    Reynod , December 14, 2011 1:30 PM
    Compatibility Issues was a useful section.

    Overall very well written.

    Cheers,
  • 0 Hide
    kd0frg , December 14, 2011 2:39 PM
    awesome information! nice work!
  • 0 Hide
    elbert , December 14, 2011 3:28 PM
    cmcghee358But the last part isn't for PSUs. It's just the last part in the series of PC components.
    Quote:
    covering efficiency and the whole 80 PLUS

    If you picked one of these books up you would want the efficiency to move them. Edition 17 was huge and very heavy. These books are already to thick for many to pick up with one hand. Scott Mueller's has published 20 editions of this book and most come with CD/DVD which may guide you to online information about the subject.

    Here is a link to his online forum.
    http://forum.scottmueller.com/
  • 0 Hide
    digiex , December 14, 2011 3:48 PM
    I'm just wondering what is the use of the floppy connector...

    Until unexpected glitch ruined the flashing if my motherboard, beyond this, I think the floppy connector is useless.
  • 4 Hide
    mayankleoboy1 , December 14, 2011 3:49 PM
    PSU: the most overlooked and underrated component
  • 4 Hide
    Anonymous , December 14, 2011 4:14 PM
    I fixed one of those non-compatible Dells way back with a standard PSU. Dell wanted £120 for a new PSU, I was suspicious, "how could they get away with that?". Checked online, found the incompatibility, dodged the bullet bought a PSU for £20 and an adapter for £5. Never bought Dell again nor recommend them.
  • 6 Hide
    A Bad Day , December 14, 2011 6:07 PM
    This reminded me of a friend who bought a $5 no-name "600 watt" PSU for a +$900 rig.

    As soon as he turned on the computer, the PSU failed so badly that it exploded into flames and took out everything: motherboard, RAM, CPU, GPU, hard drive, CD drive, you name it.
  • 0 Hide
    grantmcconnaughey , December 14, 2011 7:49 PM
    I've been reading this book lately. To me, this is absolutely the bible of PC hardware.
  • 0 Hide
    newbie_mcnoob , December 14, 2011 8:19 PM
    I remember working on an old Dell Dimension 4100 series with the proprietary power supply and RIMM memory. I'm glad those got phased out.
  • 2 Hide
    hunter315 , December 14, 2011 10:50 PM
    Quote:
    In other words, it is far better to have a single 12 V rail that can supply 40 amps than two 12 V rails supplying 20 amps each because with the single rail you don’t have to worry which connectors derive power from which rail and then try to ensure that you don’t overload one or the other.


    Im quite disappointed to see tom's fell for the marketing BS of "a single rail is better than multiple rails". On a well designed unit it does not matter one bit, the design engineers already split the connectors so the rails were reasonably balanced, and the OCP threshold is set such that added together their theoretical current limit is more than the total limit of the 12 V source so you don't have to have your rails perfectly balanced to get the full power out of your unit.

    I wrote up a post on this a while ago, if anyone has any questions or anything they think should be added to it let me know.
    Single 12V rail or multiple 12V rails? The eternal question answered


    Also, you guys left the CPU off the +12 V part of your chart of what requires what voltages.
  • 1 Hide
    PreferLinux , December 14, 2011 10:58 PM
    ChesteracorgiVery informative and interesting. The part about single 12V vs. multiple 12V rails is important reading for system builders who opt for "safer" multiple 12V PSUs. With the current state of design of PSUs anyone planning a sli or Xfire rig is well advised to opt for the single 12V design rather than risk an imbalanced PSU that overvolts a component.

    I guess it is better to be able to use the 12 V rail as an arc welder then? Because you could if you have a >1000 W single-rail PSU. Not to mention that it won't overvolt anything – how does a high power draw cause high voltages? It generally causes low voltages. And if the PSU is a decent one, the rails will be pretty well balanced, especially for SLI or Crossfire.
  • 2 Hide
    iam2thecrowe , December 14, 2011 11:15 PM
    ChesteracorgiVery informative and interesting. The part about single 12V vs. multiple 12V rails is important reading for system builders who opt for "safer" multiple 12V PSUs. With the current state of design of PSUs anyone planning a sli or Xfire rig is well advised to opt for the single 12V design rather than risk an imbalanced PSU that overvolts a component.

    you couldn't be more wrong.
Display more comments