pci-express gpu return (sink) current (gnd)

[djcristi]

hi, i was making some tests yesterday with a two 7970, and i noticed that they draw about 17amps of 12v psu 8+6 connectors but on the same connectors ground wires it only returns 5amps, the rest of the current is sinked via the pci-e connector -> motherboard lines -> atx connector gnd lines...

is this ok? soon i will receive pci-e 1x to 16x extenders and i am planning to modify them to get 12V from the psu directly rather than pci-e slot, and i am want to cut also the ground lines (A4,B4,B7) in the extender, so i hope the ground current sinks back to the pci-e 6+8 connectors to the psu, rather than to motherboard...

i'm a newbie in mining, and i have a B75M-D2V motherboard, a SPS-730M 730w psu . i am planning on installing 2x 7970 on x1 connectors. both clocked 1.13ghz @ 1.11v draws around 220W each ,

and maybe i will install another 7970 underclocked as a third gpu, and if i don't solve that ground current atx return problem , i think 3 gpu's will put around 42amps return current on atx ground lines/wires... and will burn the board/connectors quickly....

i am waiting for suggestions , thanks!

[1715696983]

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[1715696983]

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[1715696983]

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[djcristi]

up

[djcristi]

nobody knows the answer?...

[djcristi]

i also cut the GND lines on the pci 16x->16x extenders , and linked them to the molex connector (also with 12V lines), now only 3.3V is draw from the motherboard, thus protecting 1x motherboard connectors.

works fine after 3 weeks of testing