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Thread: Current sharing on mb and gpu

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    Default Current sharing on mb and gpu

    Anyone know how current sharing works with multiple power connectors on gpu's and mb's?

    I read that for gpu's the PCIe slot can provide 75w and the 6 pins are 75w each or an 8 pin at 150w.

    How is that shared on the card? Does it all just get bussed back together before going into the onboard power circuit?

    Likewise with the mb. Does the aux 12v join directly to the main psu connector 12v or just go to the CPU psu circuits?

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    Depends on the card. Depends on the motherboard.

    Some of the newer cards don't use power from the slot at all.

    Typically, the power just flows down the "path of least resistance".

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    Quote Originally Posted by jonnyGURU View Post
    Typically, the power just flows down the "path of least resistance".
    Indeed!

    That's why I wondered how all these multiple power connectors and pins can reliably work. If one goes slightly high resistance, the other burns out!



    So here's another question, is it possible to use two PC PSU's, one for the GPU and the other for the rest? I suppose you could do, only if the GPU is only using the 12v from the 6/8pin connector and nothing from the slot.

    I was wondering if using 2 cheaper psu's at say 50% 'rated' power (because they pop if you get anywhere near 100%) would get you a high power, reliable solution? (Ignoring ripple and regulation)

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    Yes. People do it all of the time.

    Not necessarily with cheaper PSUs... but "add on" PSUs are a thing. Think of the 5.25" bays that used to sell all of the time.

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    Quote Originally Posted by jonnyGURU View Post
    Yes. People do it all of the time.

    Not necessarily with cheaper PSUs... but "add on" PSUs are a thing. Think of the 5.25" bays that used to sell all of the time.
    Interesting! I didn't know that...


    OK one more question and then Ill shut up...

    How are gaming laptops with dual 1070's and i7700's running off a fanless 240w psu brick? (or don't they?) When desktop users are buying 1200w psu's for their gaming rigs?

    Thanks for having such an informative BS free forum, Jonny!

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    Quote Originally Posted by rich111 View Post
    How are gaming laptops with dual 1070's and i7700's running off a fanless 240w psu brick? (or don't they?) When desktop users are buying 1200w psu's for their gaming rigs?
    240W? 780W http://www.jonnyguru.com/forums/showthread.php?t=14056
    Best, Luca

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    Quote Originally Posted by quest for silence View Post
    This lot is running of a 330w brick...

    MSI GT83VR 6RF Titan SLI Gaming Laptop


    Processor

    6th Gen. Intel® Core™ i7-6920HQ 2.7GHz
    Turbo boost up to 3.6GHz
    Quad Core
    8MB Cache

    Memory

    64GB DDR4

    Hard Drive

    512 GB SSD
    1TB Storage (7200RPM)

    Optical Drive

    Blu Ray Writer

    Software

    Operating System: Windows 10 home 64bit

    Display

    18.4" FHD IPS level panel
    Resolution: 1920 x 1080

    Graphics

    2 x Nvidia GeForce GTX 1080 GDDR5X SLI

    Audio

    Sound by Dynaudio with Woofer
    ESS SABRE HiFi audio DAC technology
    Nahimic Audio Enhancer

    Input Devices

    Steelseries Multibacklit Gaming Keyboard

    Networking

    LAN: Killer E2400 Gigabit Ethernet with Killer Shield
    Wireless LAN: Killer Wireless-AC 1535
    Bluetooth v4.1

    Power Supply

    AC Adapter 330W
    Battery: 8-Cell

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    1080 SLI @ 330watts. It so low powered gpu .

    As the one card easily demand 180watts atleast. But mobile GPU are low powered. Not much of performance deviation though.

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    Yep. Difference between a GTX 1080 and GTX 1080 mobile. Mobile has fewer transistor, smaller die, lower base core clock (although higher boost), slower memory, lower fillrate, less memory, lower processing power and lower TDP (150W vs. 250W).

    And a Skylake H is only a 45W part.

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    There is no such thing as a GTX 1080 Mobile or GTX 1080M. The GTX 1080 for notebooks has the same GP104 GPU as the GTX 1080 for desktop. It's also using the same GDDR5X. The only difference is frequency and power consumption. That's why both are just called GTX 1080 without any suffix. Typical power consumption of a reference GTX 1080 for desktop is by the way ~165W average and ~185W peak with a heavy game, Furmark peak is also around 185W.

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