GTX980 level card: use 1 or 2 cables for pci-e connectors? - Overclock.net - An Overclocking Community

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GTX980 level card: use 1 or 2 cables for pci-e connectors?

 
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post #1 of 10 (permalink) Old 02-05-2019, 07:10 PM - Thread Starter
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GTX980 level card: use 1 or 2 cables for pci-e connectors?

another attempt to settle this once & for all:

I've a GTX980 which has 2 pci-e connector & has a TDP of around 170W which I plan to overclock but only lightly


so question's in the title: use a single pcie cable or separate pcie cables to psu?


> another question: as a general rule when a card has 2 pcie connectors, is it ok to always use a single pcie cable no matter how much the card eats (even 300W cards) or is there a "threshold" beyond which 2 cables are necessary for safety?

> and another question: does the answer to the main question also depend on the PSU used (max wattage? quality? both?) in addition to the card's TDP?

> yet another question: what's the worst that can happen if a single cable is used in such a scenario?
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post #2 of 10 (permalink) Old 02-05-2019, 07:15 PM
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Use 2. I used 1 and it caused wires to melt. Had to replace hardware due to it.

Edit: I made a thread about it years ago:
https://www.overclock.net/forum/31-p...e-burnout.html

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post #3 of 10 (permalink) Old 02-05-2019, 07:32 PM - Thread Starter
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ok

so if this is a rule that's recommended in all cases as you suggest (where card has 2 pcie connectors) then shouldn't the PSU manufacturers be sued? they all make cables with 2 pcie connectors per cable instead of one thus encouraging to use a single cable thus melting the wires (is this even legal?)
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post #4 of 10 (permalink) Old 02-05-2019, 07:41 PM
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Unless your PSU is absolute junk it shouldn't matter. I've run the XOC BIOS on my 1080 Ti and had no issues using two 8 pins on a single cable on my Focus Plus and it's how my 1080 Ti is currently running now.

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post #5 of 10 (permalink) Old 02-05-2019, 07:51 PM - Thread Starter
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Quote: Originally Posted by The Pook View Post
Unless your PSU is absolute junk it shouldn't matter. I've run the XOC BIOS on my 1080 Ti and had no issues using two 8 pins on a single cable on my Focus Plus and it's how my 1080 Ti is currently running now.
have u tried this with a real high TDP card like a GTX 590 or HD 7990?


(btw this also contradicts Bradley's topic so how did your rig survive when the wires should've melted?)
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post #6 of 10 (permalink) Old 02-05-2019, 08:06 PM
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Pook is correct here. Fried wires are due to poor crafstmanship on a poor quality PSU, or other design defect.

The wires are short enough at current gauges that the power draw we are working with in a PC won't hurt anything.

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post #7 of 10 (permalink) Old 02-05-2019, 08:17 PM
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Quote: Originally Posted by pulverizor View Post
have u tried this with a real high TDP card like a GTX 590 or HD 7990?


(btw this also contradicts Bradley's topic so how did your rig survive when the wires should've melted?)

XOC BIOS on a 1080 Ti draws at least as much power as a 590 according to Google. I was running into issues where my system was shutting off from drawing too much power with the XOC BIOS with my GPU and CPU OCed simultaneously (>750w) but with my CPU stock it was a non-issue. The cables weren't a problem, they were fine. If you run into issues your PSU is junk.

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post #8 of 10 (permalink) Old 02-06-2019, 12:18 AM
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What brand model and wattage is your PSU? unless its junk broken or you have a monster card with volt mods there is no problem using a single cable

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post #9 of 10 (permalink) Old 02-06-2019, 12:57 AM
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Passing that much current over the combined wires of one 8 pin is fine in a perfect world.
It becomes an issue when you have different gauge wires to account for, CCA PSU cables, variations is the crimps on the pins, what the crimp is made of and a connection that isn't perfect.
The voltage stays the same so as you draw more power you draw more amperage. Passing more amperage over a typical conductor raises resistance, more resistance means less voltage which means more amperage.
You can draw a lot of power over the combined copper wire used in a single 8 pin but that doesn't mean you should. Using 2 is ideal and safe. Using half the wire with about twice the resistance at the connection is not ideal but it is possible.
There is no debate on which is better but it is possible to get away with using a single 8 pin. Not sure why you'd want to do it but you can.
Quote: Originally Posted by pulverizor View Post
have u tried this with a real high TDP card like a GTX 590 or HD 7990?


(btw this also contradicts Bradley's topic so how did your rig survive when the wires should've melted?)
It's not a contradiction, both are totally possible outcomes.

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Last edited by white owl; 02-06-2019 at 01:02 AM.
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post #10 of 10 (permalink) Old 02-06-2019, 07:49 AM - Thread Starter
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Quote: Originally Posted by shilka View Post
What brand model and wattage is your PSU? unless its junk broken or you have a monster card with volt mods there is no problem using a single cable
seasonic gold can't remember the model tho

is wattage also important? (single pcie safer on a 1000W psu then on a 400W psu?)

Quote: Originally Posted by white owl View Post
There is no debate on which is better but it is possible to get away with using a single 8 pin. Not sure why you'd want to do it but you can.
because 1 pcie cable = less clutter less hassle

I already had to bring out a MOLEX cable just to feed the 3 fans on my tower (they're all controlled by a front panel off/low/high switch) that's an extra cable with 3 molex connectors just for those fans :/ waste of space
that's why wanna save on cables as much as possible

plus the PSU's at the bottom of my case so cable management not practical the whole case is cluttered with damn cables already
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