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Power chord question on a BFG 7800 GTX

post #1 of 18
Thread Starter 
I'm running an Antec TruePower 550W PSU and I have 2 BFG 7800 GTX's that I want to hook up in SLI. I just had to RMA my motherboard and disconnect everything that I put together a couple years ago (also when I only had 1 7800 GTX). The problem is that I can't remember how I had my graphics card plugged into the PSU. I've got 2 chords coming from my PSU that say PCI-E on them but I seem to remember using the Y-Cable that came with my graphics card. The Y-Cable has 2 molex connectors that go into 1 PCI-E conector. I remember I had a power complication - is it possible that the PCI-E chord coming from my PSU doesn't supply enough current for the card and that is why I needed to hook up TWO molex connectors to it? How would I look up this information? Also, considering that now I want to hook up 2 cards...if I do end up having to use the Y-Cables, that means I'll need to use FOUR molex power connections from my PSU...Is it okay if I hook a bunch together that are on the same wire as the one that goes to my optical drive, for example, or do you not get as much power that way? I don't think I have 4 SEPARATE molex wires coming from my PSU. Any help would be greatly appreciated! Thanks!
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post #2 of 18
just take the 2 PCI-E chords, and plug them into the card. If you want to use the connector you mentioned, find a regular 4 pinned power cord, connect the y chord so it has an end to fit into the 7800GTX.
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post #3 of 18
Quote:
Originally Posted by DanShap View Post
I'm running an Antec TruePower 550W PSU and I have 2 BFG 7800 GTX's that I want to hook up in SLI. I just had to RMA my motherboard and disconnect everything that I put together a couple years ago (also when I only had 1 7800 GTX). The problem is that I can't remember how I had my graphics card plugged into the PSU. I've got 2 chords coming from my PSU that say PCI-E on them but I seem to remember using the Y-Cable that came with my graphics card. The Y-Cable has 2 molex connectors that go into 1 PCI-E conector. I remember I had a power complication - is it possible that the PCI-E chord coming from my PSU doesn't supply enough current for the card and that is why I needed to hook up TWO molex connectors to it? How would I look up this information? Also, considering that now I want to hook up 2 cards...if I do end up having to use the Y-Cables, that means I'll need to use FOUR molex power connections from my PSU...Is it okay if I hook a bunch together that are on the same wire as the one that goes to my optical drive, for example, or do you not get as much power that way? I don't think I have 4 SEPARATE molex wires coming from my PSU. Any help would be greatly appreciated! Thanks!
Hooking them together on the same line isn't going to do anything except give you less molex connectors, lol. They are wired in parallel, so it's not going to give you any more power by hooking them up on the same lead...

Not sure what the amp specs are for each 7800 GTX, but 19amps on 2 12v's kinda seems low....you might have to get a new power supply if you do decide to go dual 7800GTX, but don't quote me.
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post #4 of 18
Thread Starter 
Alright but is it possible that the power cable PCI-E doesn't supply enough current for my BFG 7800 GTX?
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post #5 of 18
Quote:
Originally Posted by DanShap View Post
Alright but is it possible that the power cable PCI-E doesn't supply enough current for my BFG 7800 GTX?
If you are hooking both of those molex 4 pin connectors to the same 12v line, it could be possible, because each of your 2 12v lines supplies 19 amps...

Try hooking only your GFX card to one 12 volt line and everything else on the other and see if that helps...I don't think the 7800GTX's use more than 19amps, but i could be wrong.
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post #6 of 18
Thread Starter 
alright let's assume for a moment that the PCI-E 6 pin cables don't have enough current. I have a 12v line that goes to my optical drives that has a 4 pin connector on it and I have a DIFFERENT12v line that goes to my HDD that has a 4 pin connector as well. Couldn't I have a 4 pin from each Y-Cable going to the 2 different sources?

12v Line A --> Two 4-pin connectors attached on the same line but they each go to a different Y-Cable

12v Line B --> Two 4 pin connectors attached on the same line but they each go to a different Y-Cable

And so that way each Y-Cable will have 2 different power sources on it. Will this work?
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post #7 of 18
Quote:
Originally Posted by DanShap View Post
alright let's assume for a moment that the PCI-E 6 pin cables don't have enough current. I have a 12v line that goes to my optical drives that has a 4 pin connector on it and I have a DIFFERENT12v line that goes to my HDD that has a 4 pin connector as well. Couldn't I have a 4 pin from each Y-Cable going to the 2 different sources?

12v Line A --> Two 4-pin connectors attached on the same line but they each go to a different Y-Cable

12v Line B --> Two 4 pin connectors attached on the same line but they each go to a different Y-Cable

And so that way each Y-Cable will have 2 different power sources on it. Will this work?
I think that would work, yes. But with two cards pulling, it would probably not get enough power....but for just one, i would say, yes.
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The Crushanator
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post #8 of 18
Thread Starter 
How will I know if I hook up both and it isn't getting enough power? What are signs of this? How can I know for sure that the cards are getting the full power required? Also, can my stuff get damaged if they aren't getting enough power? THanks!
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post #9 of 18
Quote:
Originally Posted by DanShap View Post
How will I know if I hook up both and it isn't getting enough power? What are signs of this? How can I know for sure that the cards are getting the full power required? Also, can my stuff get damaged if they aren't getting enough power? THanks!
No it won't damage the cards (could put a significant load on the PSU and in due time it could fail if it is being overloaded). You would just notice that you can't overclock the cards and also that the performance isn't as good as you would have expected. I'd say open a new thread in the power supply section and ask if your PSU has enuff power for two 7800GTX's as well as your other stuff.

My guess is that it will be almost pushing it though...My computer pulls probably 450 or 500 watts at max and i only have a 850xt although it and the processor are overclocked
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The Crushanator
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post #10 of 18
If you do have to get another power supply, may i direct your attention to this one here...

http://www.newegg.com/Product/Produc...82E16817256012


It has 54amps on 1 12volt lead...more than enough to power everything you have.
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The Crushanator
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