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Can two power supplies power the same videocard?

HeXploiT

HeXploiT

Diamond Member
I have two power supplies in my rig. I am wondering if I can use a molex from each psu to power one single card? Sorry to say I don't have a grasp on electricity and how this might or might not work. Must both molex connectors come from the same psu?

Edit: I am talking about powering an 8800gts not the gtx. This is different because on the gts two molex connectors merge into one.
 
You are talking about using a Y adapter with 2 molex connectors?

It should be fine, its a parallel connection, so the voltage stays the same and the amps double. The only problem is you might be running into issues with minimum PSU load and power efficiency due to the small load on each PSU.
 
Originally posted by: JAG87
You are talking about using a Y adapter with 2 molex connectors?

It should be fine, its a parallel connection, so the voltage stays the same and the amps double. The only problem is you might be running into issues with minimum PSU load and power efficiency due to the small load on each PSU.
Click to expand...

I'm not sure I understand that. Let me explain what I'm considering.
I have two power supplies that will be powering an extremely overclocked system with two 8800gts cards. The psu's are 580(630) & 250(300) watt. I am considering using the 250watt solely to power 1 1/2 of the cards rather then just one or both. I want to do this because the 580 falls just a little short of powering the system with one card.
 
If you want to use switching power supplies in parallel, they need to be designed for that purpose, generally with diodes to prevent one supply with a slightly lower voltage from directly drawing power from the higher-voltage supply, and also to prevent some ugly problems at startup or in case of failure. I'm not sure, but I think most PC power supplies don't support this. I wouldn't do it unless the PSs specifically state suitability for parallel operation.

nBd
 
just use the 580 for system + primary card and the 250 for the secondary card.

580 is plenty for system with 1 GTS, i dunno whatt you are smoking...
 
Originally posted by: JAG87
just use the 580 for system + primary card and the 250 for the secondary card.

580 is plenty for system with 1 GTS, i dunno whatt you are smoking...
Click to expand...

Actually with the system overclocked it's not. I'm using the Hipe Type-R 580w and it took about five months to burn one of these out. Luckily Hiper replaced it for free.
Also this system has 8 120mm fans 2 dvd 2 sata 2 bay devices and 8 lights.
 
As has already been said, if you MUST use two power supplies then use the 580w to power the system and use the 250w for the molexes on the video cards. Do NOT try to mix the two power supply connectors together with a splitter. As Egon said, "It would be bad". Remember, the video cards get their power through BOTH the PCI-E slot (75w) and the 6-pin molex plug (75w). So your 250w PS is only going to be be asked to put out 150w max. If need be, you could also use it to power some of your other components (DVD drive, hard drive, lights, fans, etc).

Sounds like a bit of a mess however. Two power supplies to have mounted, twice the wiring stuffed in the case... And EIGHT 120mm fans? That seems a bit excessive. Do you really need that many? 8800GTS don't throw off THAT much heat. Besides which, they have DHES coolers on them which takes the GPU heat and throws it outside the case. So all your 120mm fans are cooling is the motherboard chipset, CPU waste heat and any other add-in cards you may have. I think you could drop a few of those fans and not notice any difference in your cooling performance. Besides which, your power supply burning out may have had NOTHING to do with the load you placed on it.

A good way to check is to run through a Power Supply Calculator. This will give you a good idea of just how much power you can expect to draw with your particular system. Once you have your numbers, you can compare it to a review of your Hiper Type R 580w PS and see if you even need the extra 250w PS.
 
Originally posted by: Creig
As has already been said, if you MUST use two power supplies then use the 580w to power the system and use the 250w for the molexes on the video cards. Do NOT try to mix the two power supply connectors together with a splitter. As Egon said, "It would be bad". Remember, the video cards get their power through BOTH the PCI-E slot (75w) and the 6-pin molex plug (75w). So your 250w PS is only going to be be asked to put out 150w max. If need be, you could also use it to power some of your other components (DVD drive, hard drive, lights, fans, etc).

Sounds like a bit of a mess however. Two power supplies to have mounted, twice the wiring stuffed in the case... And EIGHT 120mm fans? That seems a bit excessive. Do you really need that many? 8800GTS don't throw off THAT much heat. Besides which, they have DHES coolers on them which takes the GPU heat and throws it outside the case. So all your 120mm fans are cooling is the motherboard chipset, CPU waste heat and any other add-in cards you may have. I think you could drop a few of those fans and not notice any difference in your cooling performance. Besides which, your power supply burning out may have had NOTHING to do with the load you placed on it.

A good way to check is to run through a Power Supply Calculator. This will give you a good idea of just how much power you can expect to draw with your particular system. Once you have your numbers, you can compare it to a review of your Hiper Type R 580w PS and see if you even need the extra 250w PS.
Click to expand...

Thanks for the links. That's the best psu calc I've seen yet.
Came out to 632 watts with everything overclocked and my psu is 580(630 max). My case is a ThermalTake Mozart Tx hence the reason for all the fans which i must keep as they are extremely quiet, provide superior air cooling and they look real nice too. Couldn't bare to get rid of them.
Wires also aren't a problem in this case as you can plainly see. 😀
I do believe I burned the psu out by pushing the system too far but I will heed your warning here. I've decided what I will do is use the secondary psu for the main 8800gts and overclock the hell out of it while leaving the secondary videocard at stock speeds and powered by the main psu.
 
Originally posted by: Perry404
Originally posted by: Creig
As has already been said, if you MUST use two power supplies then use the 580w to power the system and use the 250w for the molexes on the video cards. Do NOT try to mix the two power supply connectors together with a splitter. As Egon said, "It would be bad". Remember, the video cards get their power through BOTH the PCI-E slot (75w) and the 6-pin molex plug (75w). So your 250w PS is only going to be be asked to put out 150w max. If need be, you could also use it to power some of your other components (DVD drive, hard drive, lights, fans, etc).

Sounds like a bit of a mess however. Two power supplies to have mounted, twice the wiring stuffed in the case... And EIGHT 120mm fans? That seems a bit excessive. Do you really need that many? 8800GTS don't throw off THAT much heat. Besides which, they have DHES coolers on them which takes the GPU heat and throws it outside the case. So all your 120mm fans are cooling is the motherboard chipset, CPU waste heat and any other add-in cards you may have. I think you could drop a few of those fans and not notice any difference in your cooling performance. Besides which, your power supply burning out may have had NOTHING to do with the load you placed on it.

A good way to check is to run through a Power Supply Calculator. This will give you a good idea of just how much power you can expect to draw with your particular system. Once you have your numbers, you can compare it to a review of your Hiper Type R 580w PS and see if you even need the extra 250w PS.
Click to expand...

Thanks for the links. That's the best psu calc I've seen yet.
Came out to 632 watts with everything overclocked and my psu is 580(630 max). My case is a ThermalTake Mozart Tx hence the reason for all the fans which i must keep as they are extremely quiet, provide superior air cooling and they look real nice too. Couldn't bare to get rid of them.
Wires also aren't a problem in this case as you can plainly see. 😀
I do believe I burned the psu out by pushing the system too far but I will heed your warning here. I've decided what I will do is use the secondary psu for the main 8800gts and overclock the hell out of it while leaving the secondary videocard at stock speeds and powered by the main psu.
Click to expand...


and the point of that is?

for SLI both cards have to run at the same clocks. if the clock is different, both cards will use the lower clock speed of the two.
 
Originally posted by: JAG87
Originally posted by: Perry404
Originally posted by: Creig
As has already been said, if you MUST use two power supplies then use the 580w to power the system and use the 250w for the molexes on the video cards. Do NOT try to mix the two power supply connectors together with a splitter. As Egon said, "It would be bad". Remember, the video cards get their power through BOTH the PCI-E slot (75w) and the 6-pin molex plug (75w). So your 250w PS is only going to be be asked to put out 150w max. If need be, you could also use it to power some of your other components (DVD drive, hard drive, lights, fans, etc).

Sounds like a bit of a mess however. Two power supplies to have mounted, twice the wiring stuffed in the case... And EIGHT 120mm fans? That seems a bit excessive. Do you really need that many? 8800GTS don't throw off THAT much heat. Besides which, they have DHES coolers on them which takes the GPU heat and throws it outside the case. So all your 120mm fans are cooling is the motherboard chipset, CPU waste heat and any other add-in cards you may have. I think you could drop a few of those fans and not notice any difference in your cooling performance. Besides which, your power supply burning out may have had NOTHING to do with the load you placed on it.

A good way to check is to run through a Power Supply Calculator. This will give you a good idea of just how much power you can expect to draw with your particular system. Once you have your numbers, you can compare it to a review of your Hiper Type R 580w PS and see if you even need the extra 250w PS.
Click to expand...

Thanks for the links. That's the best psu calc I've seen yet.
Came out to 632 watts with everything overclocked and my psu is 580(630 max). My case is a ThermalTake Mozart Tx hence the reason for all the fans which i must keep as they are extremely quiet, provide superior air cooling and they look real nice too. Couldn't bare to get rid of them.
Wires also aren't a problem in this case as you can plainly see. 😀
I do believe I burned the psu out by pushing the system too far but I will heed your warning here. I've decided what I will do is use the secondary psu for the main 8800gts and overclock the hell out of it while leaving the secondary videocard at stock speeds and powered by the main psu.
Click to expand...


and the point of that is?

for SLI both cards have to run at the same clocks. if the clock is different, both cards will use the lower clock speed of the two.
Click to expand...

Learn something new everyday.
I didn't know that as this is my first sli setup. So when I overclock with rivatuner it only shows one card. Does that mean it's actually overclocking both?
 
wow that calc shows 631watts required for my system! I've only got a 460 watt SeaSonic with 25a on the 12v rail... I havn't had a bit of stability issues yet....
 
Originally posted by: JBT
wow that calc shows 631watts required for my system! I've only got a 460 watt SeaSonic with 25a on the 12v rail... I havn't had a bit of stability issues yet....
Click to expand...

Nice. SeaSonic use superior components. Top notch psu manufacturer.
 
Originally posted by: JAG87

and the point of that is?

for SLI both cards have to run at the same clocks. if the clock is different, both cards will use the lower clock speed of the two.
Click to expand...

That's not the case if they have different stock clocks. I was able to confirm that my two GTS 640s(one stock EVGA card, one a BFG OC card) were both running at default clocks.

I don't know of any overclocking utilities that will let you overclock the cards independently, however.
 
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