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Thread: I need an 8 pin (P8) power adapter

  1. #1

    Default I need an 8 pin (P8) power adapter

    My motherboard (P55A-UD4) has an 8 pin slot for the 12v CPU power.
    My PSU only has a 4 pin (P4) for the 12v power. I'm currently using this and it's working fine. But I'd rather be on the safe side, so I'd buy something like:


    The second one seems to supply more power, so I think I'll get this one.

    Do you have any other suggestions?

    How much power does a molex connector actually supply?

    I've also seen these for cheap from some Chinese sellers, which have one more pin (a yellow cable) compared to the first one:

  2. #2
    Lsdmeasap's Avatar
    Lsdmeasap is offline GIGABYTE Guru
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    Jan 2008
    PCB Island

    Default Re: I need an 8 pin (P8) power adapter

    If you are really wanting to be on the "Safe", then an adapter is not the way to go as your PSU was not designed to deliver that much on the 12V rail to a CPU.

    Adapter will work, but it is not the safest thing to do. Your safest thing would be to buy a PSU that was designed for your board (Has 12V 8 pin EPS cable), or to only run the 4 pin cable you are using now.

    The 8 pin is really not a requirement either, although it can be used, your CPU may not pull any additional power from it anyway until you hit a super high load at high clock speeds enough to need that much power.

  3. #3

    Default Re: I need an 8 pin (P8) power adapter

    It really depends on what wattage your supply is compared the current needed by your motherboard. The extra wires in an 8 pin just help spread the current out a bit more. Putting a lot of power through 4 pins can cause a bit more voltage drop in the cables. If you have no instabilities, can run your computer without any spontaneous reboots, then you are probably ok. As far as the adapter, go with a cheap one. The difference in drop between a cheap one and the lower one is minor.

    Use a power calculator for your setup, and determine if your power supply has a bit of margin over the max power your setup will draw.
    FYI, the second one you show in the picture is a waste of money. It's the same size wires under the sleeving. And you are paying for a useless case that comes with it.

  4. #4

    Default Re: I need an 8 pin (P8) power adapter

    I later saw that the first adapter with only molex inputs was for the 8 pin PCI-E, not for the P8 motherboard input.

    So I bought the second one, the one with molex + 4pin input and the case (which.. comes very handy because I always carry the adapter with me...).

    Anyway, I bought it because I read in some places that it's safer and that plugging just the 4 pin can be dangerous:
    Even if the motherboard works with a 4 pin 12 volt cable, you are still only providing half of the current carrying capacity which would be provided by an 8 pin EPS cable. That can overheat both the motherboard connector and 4 pin cable. Scorched or melted connectors can be a result. A motherboard which has the 8 pin EPS connector expects a lot of current and you are taking a serious risk by plugging in a 4 pin cable.
    (from: All about the various PC power supply cables and connectors)

    It works fine so far, even when overclocked to 4.2 GHz and 1.375 Volts (didn't try higher than that).
    But it's a temporary solution, until I get a new PSU in the next months.

  5. #5

    Default Re: I need an 8 pin (P8) power adapter

    The possibility of scorched and melted connectors is very slight, so slight to be discounted. While I have seen melted connectors on test platforms, the fault was with a malfunctioning voltage regulator rather than the cable itself. The chances that your power supply will catastrophically fail with a big bang and smoke is much more likely, yet even the chances of that are vanishingly slim. Think on it. Out of tens of thousands of power supplies, less than one tenth of one percent ever fail. Most end up in recylcing or landfills. If you look at new motherboards, they provide an 8 pin cpu power connector, but almost all cap off the extra four pins, as it is not necessary to have the extra four pins. It is just a nicety. It helps to provide the current. That said, the wires that go to the four pin will provide the current. It is just more dense at the board than it would be if extra wires provided current to additional traces.

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