Question GPU power problem - can i 8 pin card with 8+6pin?

Current96a

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Oct 5, 2016
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Hi all. I have r9 390 that i wanna try out and probably use for some time on my PC untill i get money for better(more efficient) GPU or/and better PSU.

I use CM G550M psu with i7 6700 (non k) with 2 fans and 4 drives powered from modular molex and sata power cables. The PSU originally has only 1 fixed PCIE cable with 8pin + another 8 pin (extended) from it. But two years ago, for some reason i have cut that second 8 pin cable that came out from first 8 pin. Dont ask me why, please. Since it i used few cards, so 8 pin out i didnt cut works fine. But now i want to plug in an GPU that needs 8+6 pin (r9 390), which i dont have since i was stupid enough to cut off one of those power pins.
Now my idea is to:
  1. Use card only with 1x8 pin - which i guess it would work, but not to the potential of that card since it couldnt draw enough power.
  2. Use molex / sata power cables adapted to 6 pin gpu power. - Which im thinking are suitable to cover for 75W 6pin cable
  3. Use 5 pin out on my psu thats ment for molex / sata modular power cables and get it to 6pin. - I have seen online some similar cables for modular psus that go to 6 pin pcie, tho i cant find anything similar for sale. But since they are built for molex / sata power cables ment for drives and fans, then i guess it would be the same as adapting from molex / sata to 6 pin, right? What if i used 2 of those 5 pin outs with modular cables that came with my psu, and get 1 molex or sata out from each of those cable to go to 1 6pin and to gpu. I saw many 6 pin adapters that go from 2 molexes instead of just one.

Please dont:
  • Strive away from topic and what info i am trying to get so you would tell me how i need to change psu, gpu, pc or whatever. I came for tech tips and talk to try and see if anything can be managed here and whats the best way of doing it - if doing it. If i were in position to buy new adequate psu for 300W card, i would gladly invest that money in gpu that is of same or better performance while it spends less power and needs less pcie cables.
  • Tell me how 550w isnt enough ,since a personal friend of mine used safely fx 6300 (95W) and r9 290 on similar 500w psu for 2 years until he sold it, at which point it was also working.
 
1. Might work. You'll have to use a splitter to make it 2(6+2) cables. As the card likely won't turn on without both connectors used. The danger is too much current, melting cables, fire. If this was one of those double 8 pin cables from the get go. It should be rated for a dual 8pin load. But I won't guarantee.

2. May work. Only use molex and only use two separate molex strands. SATA can't handle the current which molex can. Still there is a risk of overloading the lines depending on the 6pin draw. See danger above.

3. Sounds a lot like two. So same diff. Only use PSU cables made for said PSU. Other makes models may have different PSU side pin outs.
 
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Current96a

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Oct 5, 2016
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1. Might work. You'll have to use a splitter to make it 2(6+2) cables. As the card likely won't turn on without both connectors used. The danger is too much current, melting cables, fire killing everyone in your house. If this was one of those double 8 pin cables from the get go. It should be rated for a dual 8pin load. But I won't guarantee.

2. May work. Only use molex and only use two separate molex strands. SATA can't handle the current which molex can. Still there is a risk of overloading the lines depending on the 6pin draw. See danger above.

3. Sounds a lot like two. So same diff. Only use PSU cables made for said PSU. Other makes models may have different PSU side pin outs.
Thank you for your answer. It helps a lot, and i know now how to do it if i decide to go with molex, and even if i decide to do it.

But, please if you can, see the picture below. That's the psu that i have. As you can see 1x8 pin (6+2) comes out of psu with 8 cables that enter in 8 pin plastic and then from those same 8 cable enterances there are another 8 coming out that go to another 8pin (6+2).

So you think that i could put 8 pin adapter to 2x8pin or 1x8+1x6 pin and make it work? I mean i was thinkiing of it also kinda cause that cable i guess it was intended to be able to provide 300w. So i guess it should be able to be splited into 2 x8 pin (like it kinda was from factory) so that gpu would get 150w on each 8 pin connector, and not whole 300W on just one. If this is ok option also, i then should just have to decide if i should go for molex or this one, aka which was less hazardous.

ps all of this would be temporary, so i guess it wont hurt ether way. But still i wanned to see which was the best way to do it if i go for it.

ty for your attention again tho.

 

clutchc

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Herald
+1 on not using the SATA connectors. Pins/connectors will burn up.
If using Molex to PCIe, get an adapter that uses 2 x Molex. And be sure to plug them into Molex connectors on separate daisy-chains. Not the best setup, but it will work and be safe.
 

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