ATX supply w/adapter to 4 pin CPU power?

Discussion in 'Asus' started by me, May 4, 2010.

  1. me

    me Guest

    I have a P4P800 I want to install into a box with an older PS. (I do
    plan to check to see if there are enough watts in the PS for the new
    setup).

    Question: Can I put a molex -> "CPU 4 pin" adapter on a power
    connector safely? Do the built in 4-pin connectors have larger gauge
    wire for more amps than you normally pull through molex connectors? Or
    are they just another connector on the same gauge wire as normal?
    me, May 4, 2010
    #1
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  2. me wrote:
    > I have a P4P800 I want to install into a box with an older PS. (I do
    > plan to check to see if there are enough watts in the PS for the new
    > setup).
    >
    > Question: Can I put a molex -> "CPU 4 pin" adapter on a power
    > connector safely? Do the built in 4-pin connectors have larger gauge
    > wire for more amps than you normally pull through molex connectors? Or
    > are they just another connector on the same gauge wire as normal?
    >

    I would be leery of using an adapter as the 4 pin connector provides two
    12 volt and two common connections to power the CPU. As the older
    motherboards mainly support processors with much higher power demands
    than the newer ones it will place a much higher demand on the connection
    and having an adapter just adds another point of failure. I am not even
    sure that a 4 pin molex can supply the 100+ watts on the 12 volt line
    needed for some of the older processors.
    Michael W Ryder, May 4, 2010
    #2
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  3. me

    Paul Guest

    me wrote:
    > I have a P4P800 I want to install into a box with an older PS. (I do
    > plan to check to see if there are enough watts in the PS for the new
    > setup).
    >
    > Question: Can I put a molex -> "CPU 4 pin" adapter on a power
    > connector safely? Do the built in 4-pin connectors have larger gauge
    > wire for more amps than you normally pull through molex connectors? Or
    > are they just another connector on the same gauge wire as normal?
    >


    You would need to go from two Molex disk drive connectors, to one ATX12V.
    Each Molex would be on its own cable. You would not put other loads on
    the same Molex, such as disk drive connectors (the voltage drop on 12V
    would be upsetting the disk drive, rather than the Vcore regulator which would
    not care so much).

    PSU --------X---X---Y
    \
    +-----Z Adapter. Y=Molex, Z=ATX12V
    /
    PSU --------X---X---Y (Using two Molex chains to get enough 12V amps.)

    What that would give you, is 6 to 8 amps to play with, on each Molex.
    Or 12V * (6A + 6A) for a total of 144W. 144W flowing to Vcore, with
    a conversion efficiency of 90%, gives enough power for a 130W processor.
    If your S478 processor uses less than 130W, then the two Molex feel less
    stress.

    The current sharing on the wires, is not guaranteed. It depends on
    the path resistance of each path. Say one Molex was making a bad connection
    on its yellow wire. That would cause the other Molex to carry more of the
    total load. At a high enough current flow level, the Molex pin can burn.

    Then, you have to check the label on the power supply. Say your power supply
    is 12V @ 15A, which I consider a minimum for an S478 computer. If you used
    a 130W S478 processor, now you have about 3 amps left. 0.6A for disk drive on
    12V, 1.5A for CDROM on 12V, 0.5A for fan cooling from 12V, takes 2.6A. Now your
    margin is 0.4A, which is cutting it too close to the capacity limit of the supply.

    Generally speaking, the power supply itself probably doesn't have the
    capacity needed, if the necessary wiring is missing. It kinda works that
    way on PCI Express as well. If a power supply has no PCI Express video card
    connectors, then by the time you analyze the available power on the supply,
    there really aren't enough Molex cables, enough current capacity on 12V,
    to make the usage of adapters that good a prospect.

    So yes, you can use adapters, but do the math and consider how close to
    any limit, you might be getting.

    In this picture, is an adapter. But notice they're only using one Molex.
    That means the max 8 amps from the molex, can supply up to 96W to the
    regulator for Vcore. 96W * 90% = 86.4W for the processor itself.

    http://www.playtool.com/pages/psuconnectors/12v4pinadapter.jpg

    You can use the part number for the processor, and look it up here,
    to find out what power it uses.

    http://processorfinder.intel.com

    You really want an adapter like that, to be using two Molex, to give
    you more headroom. To some extent, the scheme also depends on the Molex.
    I've noticed a decline in the quality of Molex connectors. The one that
    burned on my video card, never fit quite right, and required a lot of
    wiggling to get the pins centered. The Molex (mini-fit jr) used to be
    a reliable connector, but I wonder if the patent expired, and any
    hillbilly can make them now ?

    This one isn't quite right either. This is two Molex to a 2x4, whereas
    you'd want two Molex to a 2x2.

    http://www.playtool.com/pages/psuconnectors/epsadapter.jpg

    You can make your own adapter cable. For example, snip this extender cable
    in two, cut up some Molex Y cables, should give you enough connectors and
    wires to make an adapter. You wire up black and yellow wires, to make the
    ATX12V. I use "shrink wrap tubing" or polyolefin tubing, to cover
    any bare wires, on home brew connectors. The tubing shrinks under hot air -
    and works fine as long as you don't overdo it, and melt the insulation
    on the wires themselves.

    http://www.startech.com/item/ATXP4EXT-8-ATX12V-4-Pin-P4-CPU-Power-Extension.aspx

    I get shrink wrap tubing at a local electronics store (not RadioShack). I
    keep about five different sizes. The tubing should be a bit larger than
    the thing you're insulating - you don't want to have to force
    it into the tubing. It is easy to buy too small a tube for a project,
    and have to go back and buy the next biggest size (happens to me all the
    time).

    http://heatshrinktubing.net/content/view/18/32/

    Paul
    Paul, May 4, 2010
    #3
  4. me

    me Guest

    On Tue, 04 May 2010 08:02:08 -0400, Paul <> wrote:

    >me wrote:
    >> I have a P4P800 I want to install into a box with an older PS. (I do
    >> plan to check to see if there are enough watts in the PS for the new
    >> setup).
    >>
    >> Question: Can I put a molex -> "CPU 4 pin" adapter on a power
    >> connector safely? Do the built in 4-pin connectors have larger gauge
    >> wire for more amps than you normally pull through molex connectors? Or
    >> are they just another connector on the same gauge wire as normal?
    >>

    >
    >You would need to go from two Molex disk drive connectors, to one ATX12V.
    >Each Molex would be on its own cable. You would not put other loads on
    >the same Molex, such as disk drive connectors (the voltage drop on 12V
    >would be upsetting the disk drive, rather than the Vcore regulator which would
    >not care so much).
    >
    > PSU --------X---X---Y
    > \
    > +-----Z Adapter. Y=Molex, Z=ATX12V
    > /
    > PSU --------X---X---Y (Using two Molex chains to get enough 12V amps.)
    >
    >What that would give you, is 6 to 8 amps to play with, on each Molex.
    >Or 12V * (6A + 6A) for a total of 144W. 144W flowing to Vcore, with
    >a conversion efficiency of 90%, gives enough power for a 130W processor.
    >If your S478 processor uses less than 130W, then the two Molex feel less
    >stress.
    >
    >The current sharing on the wires, is not guaranteed. It depends on
    >the path resistance of each path. Say one Molex was making a bad connection
    >on its yellow wire. That would cause the other Molex to carry more of the
    >total load. At a high enough current flow level, the Molex pin can burn.
    >
    >Then, you have to check the label on the power supply. Say your power supply
    >is 12V @ 15A, which I consider a minimum for an S478 computer. If you used
    >a 130W S478 processor, now you have about 3 amps left. 0.6A for disk drive on
    >12V, 1.5A for CDROM on 12V, 0.5A for fan cooling from 12V, takes 2.6A. Now your
    >margin is 0.4A, which is cutting it too close to the capacity limit of the supply.
    >
    >Generally speaking, the power supply itself probably doesn't have the
    >capacity needed, if the necessary wiring is missing. It kinda works that
    >way on PCI Express as well. If a power supply has no PCI Express video card
    >connectors, then by the time you analyze the available power on the supply,
    >there really aren't enough Molex cables, enough current capacity on 12V,
    >to make the usage of adapters that good a prospect.
    >
    >So yes, you can use adapters, but do the math and consider how close to
    >any limit, you might be getting.
    >
    >In this picture, is an adapter. But notice they're only using one Molex.
    >That means the max 8 amps from the molex, can supply up to 96W to the
    >regulator for Vcore. 96W * 90% = 86.4W for the processor itself.
    >
    >http://www.playtool.com/pages/psuconnectors/12v4pinadapter.jpg
    >
    >You can use the part number for the processor, and look it up here,
    >to find out what power it uses.
    >
    >http://processorfinder.intel.com
    >
    >You really want an adapter like that, to be using two Molex, to give
    >you more headroom. To some extent, the scheme also depends on the Molex.
    >I've noticed a decline in the quality of Molex connectors. The one that
    >burned on my video card, never fit quite right, and required a lot of
    >wiggling to get the pins centered. The Molex (mini-fit jr) used to be
    >a reliable connector, but I wonder if the patent expired, and any
    >hillbilly can make them now ?
    >
    >This one isn't quite right either. This is two Molex to a 2x4, whereas
    >you'd want two Molex to a 2x2.
    >
    >http://www.playtool.com/pages/psuconnectors/epsadapter.jpg
    >
    >You can make your own adapter cable. For example, snip this extender cable
    >in two, cut up some Molex Y cables, should give you enough connectors and
    >wires to make an adapter. You wire up black and yellow wires, to make the
    >ATX12V. I use "shrink wrap tubing" or polyolefin tubing, to cover
    >any bare wires, on home brew connectors. The tubing shrinks under hot air -
    >and works fine as long as you don't overdo it, and melt the insulation
    >on the wires themselves.
    >
    >http://www.startech.com/item/ATXP4EXT-8-ATX12V-4-Pin-P4-CPU-Power-Extension.aspx
    >
    >I get shrink wrap tubing at a local electronics store (not RadioShack). I
    >keep about five different sizes. The tubing should be a bit larger than
    >the thing you're insulating - you don't want to have to force
    >it into the tubing. It is easy to buy too small a tube for a project,
    >and have to go back and buy the next biggest size (happens to me all the
    >time).
    >
    >http://heatshrinktubing.net/content/view/18/32/
    >
    > Paul


    Thanks for all the detail. After redoing the calculations with some of
    your info and the PSU calculator here:
    http://extreme.outervision.com/PSUEngine

    .... I think I'm too close to the limit on the PS's I have anyway. I
    will have to upgrade.
    me, May 4, 2010
    #4
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