Power supply units; 24 pin VS 20+4 pin
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Thread: Power supply units; 24 pin VS 20+4 pin

  1. #1
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    Power supply units; 24 pin VS 20+4 pin

    What's the difference between a 24 pin PSU and a 20+4 pin PSU? Aside from the fact the 24 pin PSU really only has 23 pins that make a connection and one that's blank, I am clueless. Is the 20+4 pin PSU just a versatile PSU? Can be 20 or 24 depending on your mobo? Help!

  2. #2
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    it depends on the motherboard. newer atx boards and workstation boards have 24 pin connectors. most of the new psus will have a 24 pin with a detachable 4 pin section to convert to a 20 pin

  3. #3
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    Yeah, power supplies with 24pin connectors allow you to detach the extra 4 pins to work with older motherboards. The only problem with some of the wording they use is that there is still a 4pin AUX connection to the board in another location. Your best bet is to check the actual connection type on the PS cables. Everything above suggests that retailers just might mislabel things by mistake.
    Give what you cannot keep to gain what you cannot lose.

  4. #4
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    My Intel DG965RY motherboard comes with a 24-pin ATC connector but still requires the 4-pin power connector near the CPU. However, the PSU I had was a 20-pin one, and it works fine without any problems. Maybe if I had multiple graphics cards, then the 24-pin one will be required. Otherwise 20-pin is OK. But check the mobo manual.

  5. #5
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    Quote Originally Posted by Anusha
    My Intel DG965RY motherboard comes with a 24-pin ATC connector but still requires the 4-pin power connector near the CPU.
    Yeah my mobo also need the aux connector. Some older motherboards used to have a 4pin aux connector plus another aux power connector that was similar to AT P8/P9 connectors. Im using a 24pin power supply + aux, though I donno what good the extra 4pins does. My core voltage keeps fluctuating.
    I've heard that some PCIx card needs an additional 6pin power connector. can these graphic cards work without extra power?
    Last edited by Wreckles; December 16th, 2006 at 10:38 AM.
    Main Rig: Intel Pentium D820, Intel DG965RY, Kingston 1.5GB DDR2 @667, Sapphire X850XT 558/600, Samsung 80GB SATAII, ASUS 18X DVD-RW LightScribe SATA, 19" ViewSonic LCD, Wi-Fi

  6. #6
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    Quote Originally Posted by Wreckles
    Yeah my mobo also need the aux connector. Some older motherboards used to have a 4pin aux connector plus another aux power connector that was similar to AT P8/P9 connectors. Im using a 24pin power supply + aux, though I donno what good the extra 4pins does. My core voltage keeps fluctuating.
    I've heard that some PCIx card needs an additional 6pin power connector. can these graphic cards work without extra power?
    Your motherboard also need the aux connector because both of us have the same motherboard lol.

    I don't understand why your core voltage keeps on fluctuating, because the D820 CPU doesn't support EIST hence doesn't lower the core voltage when the CPU is idle.

    Some video cards allow you to not connect the power connector, but it would run slower than the default specs. I don't know this for sure though. Some video cards require the power connector, otherwise it would display an error on screen before POSTing (it doesn't POST in fact) saying that the external power connector is not connected.

    I believe the extra 4-pins in the 24-pin connector is for the stability of the highend PCI-E cards (especially when multiple cards are running in parallel). Maybe to lower the stress of the power suplpy unit. Most probably they powering from a different rail other pins. Just a thought.

  7. #7
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    When idle my core voltage changes between 1.31 and 1.34
    Under load it drops to 1.30 - 1.32
    Will this effect the lifetime of my CPU ?

    and Im planning on buying a X850XT graphic card. Heard that the X800 line needs the additional 6pin power connector.. But my PSU dosent have one so I guess I'll have to buy a converter..
    Last edited by Wreckles; December 17th, 2006 at 01:02 AM.
    Main Rig: Intel Pentium D820, Intel DG965RY, Kingston 1.5GB DDR2 @667, Sapphire X850XT 558/600, Samsung 80GB SATAII, ASUS 18X DVD-RW LightScribe SATA, 19" ViewSonic LCD, Wi-Fi

  8. #8
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    I doubt it will hurt your CPU, since they are designed to tolerate a decent variance in voltage. It's petty hard to have a perfectly stable vcore. To put it into perspective, your vcore is only fluctuating +/-2%. That's not a big deal, IMO.
    Give what you cannot keep to gain what you cannot lose.

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    If it is not overclocked, lower voltage is better than the default voltage!!! (1.35V is the default right?)

  10. #10
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    Quote Originally Posted by ThreeOnTheTree
    I doubt it will hurt your CPU, since they are designed to tolerate a decent variance in voltage. It's petty hard to have a perfectly stable vcore. To put it into perspective, your vcore is only fluctuating +/-2%. That's not a big deal, IMO.
    Glad to hear that kinda fluctuating will do no harm. But it'll probably increase when I add in my X850 ?


    Quote Originally Posted by Anusha
    If it is not overclocked, lower voltage is better than the default voltage!!! (1.35V is the default right?)
    Max voltage listed on the box was 1.4V and its not overclocked (I happened to have a DG965RY by the way.. )
    I thought the vcore voltage should get higher under load?
    Last edited by Wreckles; December 17th, 2006 at 12:11 PM.
    Main Rig: Intel Pentium D820, Intel DG965RY, Kingston 1.5GB DDR2 @667, Sapphire X850XT 558/600, Samsung 80GB SATAII, ASUS 18X DVD-RW LightScribe SATA, 19" ViewSonic LCD, Wi-Fi

  11. #11
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    Quote Originally Posted by Wreckles
    Glad to hear that kinda fluctuating will do no harm. But it'll probably increase when I add in my X850 ?
    How would the CPU voltage increase when you add a video card? If it does, then there's something wrong with the motherboard/power supply. It means, they can't work well under load.

    Max voltage listed on the box was 1.4V and its not overclocked (I happened to have a DG965RY by the way.. )
    I thought the vcore voltage should get higher under load? [/QUOTE]

    Forgot
    You CPU doesn't support EIST, so it doesn't change the voltage. But mine, for example, goes down to 0.85V I guess, when the CPU is idle and if I have EIST enabled. Default voltage is around 1.35V.

  12. #12
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    Quote Originally Posted by Anusha
    How would the CPU voltage increase when you add a video card? If it does, then there's something wrong with the motherboard/power supply. It means, they can't work well under load.
    I meant the increase of fluctuation..
    Anyways Im not so sure about if my cheap power supply will be able to handle the load..
    Main Rig: Intel Pentium D820, Intel DG965RY, Kingston 1.5GB DDR2 @667, Sapphire X850XT 558/600, Samsung 80GB SATAII, ASUS 18X DVD-RW LightScribe SATA, 19" ViewSonic LCD, Wi-Fi

  13. #13
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    Quote Originally Posted by Wreckles
    I meant the increase of fluctuation..
    Anyways Im not so sure about if my cheap power supply will be able to handle the load..
    When the total system power requirement increases, usually the CPU voltage is not affected even if the power supply is shabby. This is because of the voltage regulators in the motherboard. But if the +12V, +5V, +3.3V values dip too much, this could lead to all sorts of troubles.

  14. #14
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    Got my X850XT today..
    No problems so far, no fluctuation increase. External power connector was required, but the converter was supplied with the card. So I guess my PSU can handle it.
    Main Rig: Intel Pentium D820, Intel DG965RY, Kingston 1.5GB DDR2 @667, Sapphire X850XT 558/600, Samsung 80GB SATAII, ASUS 18X DVD-RW LightScribe SATA, 19" ViewSonic LCD, Wi-Fi

  15. #15
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    Older ATX board used to have 20 pin for the AMD Athlon XP. The P4 on the other hand need an extra 2x12v (2x12 and 2xGND) connector that can be mistaken for 20+4. What 20+4 meen is, that Motherboard as a 24 pin configuration and not a 20 pin. So compagnie made PSU to support both kind of ATX standard. So the PSU has a standard 20 pin plus an extra 4 pin for the power socket.

    Today, I wont say all but most have the new 24 pin standard. So new PSU comes in 24 pin. Basickly 20+4 PSU were designed to hepl the conversion from 20 to 24.
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