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My PSU do not have PCI-E power cable

Need help.

I have 500W PSU without PCI-E power cable. I need to power up my ASUS GTX 680, which need 300W additional 6+8 pin PCIe power - from the wesbite. So, can I use molex 4 pin to PCI-E power connector to connect to my GPU? Is it enough?
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  1. If it does not have a PCI-E cable, It probably cannot put out enough current.

    How many amps on the 12v rail?
  2. smeezekitty said:
    If it does not have a PCI-E cable, It probably cannot put out enough current.

    How many amps on the 12v rail?


    sorry but how to check it?
  3. Check the PSU label, you must have something like this:

    "Output +3.3V@30A, +5V@30A, +12V@62A, -12V@0.8A, +5VSB@3.0A1"

    What you seek are the Amps at the +12V
  4. juanrdp said:
    Check the PSU label, you must have something like this:

    "Output +3.3V@30A, +5V@30A, +12V@62A, -12V@0.8A, +5VSB@3.0A1"

    What you seek are the Amps at the +12V


    one 20A and one 18A
  5. popobe said:
    juanrdp said:
    Check the PSU label, you must have something like this:

    "Output +3.3V@30A, +5V@30A, +12V@62A, -12V@0.8A, +5VSB@3.0A1"

    What you seek are the Amps at the +12V


    one 20A and one 18A


    For 300w you need 25A (at 12v), as you have two diferent rails it would work if you put a molex to 8pin in one rail and the molex to 6 pin in the second rail, if you put both in the same rail your PSU isn't enought.
  6. juanrdp said:
    popobe said:
    juanrdp said:
    Check the PSU label, you must have something like this:

    "Output +3.3V@30A, +5V@30A, +12V@62A, -12V@0.8A, +5VSB@3.0A1"

    What you seek are the Amps at the +12V


    one 20A and one 18A


    For 300w you need 25A (at 12v), as you have two diferent rails it would work if you put a molex to 8pin in one rail and the molex to 6 pin in the second rail, if you put both in the same rail your PSU isn't enought.


    my PSU got 2 output for molex :
    - 2x molex 4-pin
    - 1x molex 4-pin + 1x sata

    i read somewhere it is dangerous to use 1 molex 4pin to PCI-e 6 pin, and they recommend use 2 molex to PCI-e 6 pin.

    is there any molex 4pin to 8 pin PCI-e connector sell in market?

    What you recommend to get my GPU works? Thanks very much :)
  7. Best answer
    When i said molex to 6 or 8 pin i was reallly saying 2 Molex to 6pin or 2 Molex to 8 Pin, i never see a single Molex to 6/8 Pin conector.

    In yor current PSU you could use 2 Molex (- 2x molex 4-pin) to power the 8pin connector, but then have a couple of little problems:

    - Need to ensure that the - 1x molex 4-pin + 1x sata is in a second diferent rail
    - To power the 6 pin you really only have a single Molex, the problem is that a single molex is 60w and the 6pin 75w you could use a second molexfrom the sata to be safe.
  8. juanrdp said:
    When i said molex to 6 or 8 pin i was reallly saying 2 Molex to 6pin or 2 Molex to 8 Pin, i never see a single Molex to 6/8 Pin conector.

    In yor current PSU you could use 2 Molex (- 2x molex 4-pin) to power the 8pin connector, but then have a couple of little problems:

    - Need to ensure that the - 1x molex 4-pin + 1x sata is in a second diferent rail
    - To power the 6 pin you really only have a single Molex, the problem is that a single molex is 60w and the 6pin 75w you could use a second molexfrom the sata to be safe.


    haha thanks so much, now i got it.

    so i just need to find:
    1. 2 Molex to 8pin PCI-e
    2. 2 Molex to 6pin PCI-e
    3. 1 sata to 4pin molex

    Correct?
  9. it would be better to get a new psu with actual pcie 6x power connectors, especially since you are trying to power a high end graphics card, you will most likely either kill your psu or it will just not work.
  10. Yes that corrent, but don't forget that's only works while the 2 molex and the molex-sata are in the two diferent rails of 12v.

    Check that the second 12v rail isn't used in a 4 pin board conection.
  11. mauller07 said:
    it would be better to get a new psu with actual pcie 6x power connectors, especially since you are trying to power a high end graphics card, you will most likely either kill your psu or it will just not work.


    yes i know this would be better solution earlier, and i already own a compatible PSU for my graphic card but i dont bring it back home from college as it heavy. Just want to try find other solution without buying a new 2nd PSU, so i want to try if there possible way to use my old PSU at home. Thanks for the recommendation :)
  12. juanrdp said:
    Yes that corrent, but don't forget that's only works while the 2 molex and the molex-sata are in the two diferent rails of 12v.

    Check that the second 12v rail isn't used in a 4 pin board conection.


    yes both of them are in different rail as i checked it and they are free to use

    thanks so much you helped me lot on understanding these power supply things! :D
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