PSU modular cables - Are PCIe cables swappable?

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  1. Posts : 219
    Win 10, Win 7 & KDE Neon
       #1

    PSU modular cables - Are PCIe cables swappable?


    Hey all.

    I have recently been in receipt of a gtx 1070, a nice little upgrade over my gtx 660 ( I know, but it works well ).

    Upon installation, I realised I only have a 6pin to 6pin PCIe on my 850W CoolerMaster PSU ( Cooler Master Real Power M850 RS-850-ESBA ), which is now about 12 years old. Along the way, I have lost my CoolerMaster 8 pin PCIe cable which I need for the gtx 1070. In my studio, I know I have a 6+2pin PCIe cable that belongs to a Corsair CX750 ( I think its a CX ).

    Are PCIe modular cables interchangeable between different brands, I remember reading a while back it can be a bit dicey, so thought I would check, get some advice, before trying......Alternatively, would a 6 to 8 pin adapter work just as well?

    Thanks in advance.
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  2. Posts : 8,633
    Mac OS Catalina
       #2
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  3. Posts : 7,088
    Windows 10 Pro 64 bit
       #3

    Generally modular PSU cables between manufacturers are not compatible nor necessarily cables between different PSUs from the same manufacturer.
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  4. Posts : 219
    Win 10, Win 7 & KDE Neon
    Thread Starter
       #4

    @bro67 thank you for the link, so I have a type 3 PCIe cable on the 750 CX - I did google it but missed this. ' Google is your friend' is not helpful
    @Steve C I thought as much. I won't risk it.

    I contacted Cooler Master and they told me they no longer have the PCIe cables for that unit in stock anymore. Oh Well.

    Will the 6pin to 8pin adapter work? or is that a red herring.
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  5. Posts : 2,280
    Windows 10
       #5

    Will the 6pin to 8pin adapter work? or is that a red herring.
    That you will have to check yourself. Look at what is connected to what in the adapter and check with a multimeter.
    The 6 pin is 75 w capacity, the 8 pin 150 w. So you need to consider the power requirements of your particular Graphics Card.

    GTX 1070 is a 150 w Card so you would get more volts drop on the 6 pin cable and it would run warmer at maximum wack, twice the rated current. That is the risk you take.

    Potentially you can use two 6 pin cables, but that depends on the PSU design, again that you will have to find out yourself.

    This is an electronics engineer answer not a gamer geek answer.
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  6. TV2
    Posts : 2,010
    W10 Pro 20H2
       #6

    This article here explains the 6-pin - 8-pin wiring very well. Read the post at the very bottom for a complete explanation.
    connector - What are "sense" pins in 8-pin PCI Express power plug? - Electrical Engineering Stack Exchange

    In summary it states that a 6-pin to 8-pin adapter, made for PCI-e, will work.
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  7. Posts : 219
    Win 10, Win 7 & KDE Neon
    Thread Starter
       #7

    Helmut said:
    That you will have to check yourself. Look at what is connected to what in the adapter and check with a multimeter.
    The 6 pin is 75 w capacity, the 8 pin 150 w. So you need to consider the power requirements of your particular Graphics Card.

    GTX 1070 is a 150 w Card so you would get more volts drop on the 6 pin cable and it would run warmer at maximum wack, twice the rated current. That is the risk you take.

    Potentially you can use two 6 pin cables, but that depends on the PSU design, again that you will have to find out yourself.

    This is an electronics engineer answer not a gamer geek answer.
    Thank you. I am not really a gamer, but, I developing some VR Galleries using Unity.

    Obviously, I will not hold anyone liable if it all goes wrong ( I don't think it will ) I just looking for experienced information.

    I do have an extra 6 pin for that PSU. I will look into it. I could swap in the CX750 and see if there are any real world benefits to a GTX1070 over GTAX660 for my usage.

    - - - Updated - - -

    TV2 said:
    This article here explains the 6-pin - 8-pin wiring very well. Read the post at the very bottom for a complete explanation.
    connector - What are "sense" pins in 8-pin PCI Express power plug? - Electrical Engineering Stack Exchange

    In summary it states that a 6-pin to 8-pin adapter, made for PCI-e, will work.
    Many thanks TV2
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  8. TV2
    Posts : 2,010
    W10 Pro 20H2
       #8

    Yeah, all that the 7&8 pins do is tell the device that the power supply is capable of supplying 150W to the +12 leads.
    Without the Sense pin the device won't turn on.

    You need to confirm that your power supply can deliver 150W to the line.
    Otherwise you could damage the card.
    Just adding a second 6-pin to the mix does nothing if it can't deliver the goods. And adding +12v to the sense pin on the card will most definitely fry it good. (Don't do that!)
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  9. Posts : 219
    Win 10, Win 7 & KDE Neon
    Thread Starter
       #9

    TV2 said:
    Yeah, all that the 7&8 pins do is tell the device that the power supply is capable of supplying 150W to the +12 leads.
    Without the Sense pin the device won't turn on.

    You need to confirm that your power supply can deliver 150W to the line.
    Otherwise you could damage the card.
    Just adding a second 6-pin to the mix does nothing if it can't deliver the goods. And adding +12v to the sense pin on the card will most definitely fry it good. (Don't do that!)
    Thanks for the info TV2.

    I have 6 +12v on the psu. 4 are +12v peak @18 and 2 are +12v peak@28.

    PSU modular cables - Are PCIe cables swappable?-img_20200702_054405.jpg
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  10. TV2
    Posts : 2,010
    W10 Pro 20H2
       #10

    So you look good to go with the adapter.
    18A @ 12v = 216W
    28A @ 12v = 336W
    So regardless of how the PCI-e cable is wired it should be able to delver the minimum 150W needed.
    (Insert all appropriate legal disclaimer here)
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