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I purchased 2 7970s a couple hours ago, and they'll most likely be here be Thursday. I see that for power it has one 6 pin and one 8 pin port. I'm out of 8 pins and I only have 1 6 to 8 pin adapter. I read somewhere though that 8 pin isn't totally necessary to power a video card and that I could just use 2 6 pins. Is this true? If so, are there any drawbacks to doing this?
 

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Originally Posted by Jov4nTh3Yu9o View Post

I purchased 2 7970s a couple hours ago, and they'll most likely be here be Thursday. I see that for power it has one 6 pin and one 8 pin port. I'm out of 8 pins and I only have 1 6 to 8 pin adapter. I read somewhere though that 8 pin isn't totally necessary to power a video card and that I could just use 2 6 pins. Is this true? If so, are there any drawbacks to doing this?
6 pin PCI-express cable provides 75 watts. The PCI-express slot provides 75 watts (in gen2, not sure if that has been increased for gen3). The 8 pin PCI-express cable provides 150 watts. The Radeon HD 7970 eats 250 watts according to wikipedia. If you end up using that 6 to 8 pin adapter, you will be providing 75+75+75=225 watts to the GPU, 25 short of the TDP. You may run into serious issues when the card is being stressed to the max such as rebooting and shutdowns due to lack of adequate power.

Long story short, you will almost definitely need real 8 pin pci-express cables.
 

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You need the 8pin.
 

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Originally Posted by Jov4nTh3Yu9o View Post

Alright so if I get a 6 to 8 or 4 to 8 pin adapter... I'll be ok right?
I haven't used adapters for my gpus, but it should work.
 
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Originally Posted by Jov4nTh3Yu9o View Post

Alright so if I get a 6 to 8 or 4 to 8 pin adapter... I'll be ok right?
Doubt it. As I mentioned above, the 6 pins only provide 75 watts. You can't make it provide 150 watts by attaching an 8 pin adapter to it. You'll need the 8 pin to come straight from the power supply.

The adapter will work, but when you stress the card, you put the PC at risk of crashing.
 

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Discussion Starter · #11 ·
Quote:
Doubt it. As I mentioned above, the 6 pins only provide 75 watts. You can't make it provide 150 watts by attaching an 8 pin adapter to it. You'll need the 8 pin to come straight from the power supply.

The adapter will work, but when you stress the card, you put the PC at risk of crashing.
I mean... The cards themselves come with adapters 4 to 8 and 6 to 8.. If what u say is true, then there would be no point in providing them at all.
 

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Quote:
Originally Posted by Jov4nTh3Yu9o View Post

Quote:
Doubt it. As I mentioned above, the 6 pins only provide 75 watts. You can't make it provide 150 watts by attaching an 8 pin adapter to it. You'll need the 8 pin to come straight from the power supply.
The adapter will work, but when you stress the card, you put the PC at risk of crashing.
I mean... The cards themselves come with adapters 4 to 8 and 6 to 8.. If what u say is true, then there would be no point in providing them at all.
Just took a look at pics of packaging for a Sapphire model, and you are correct. It should work for you if they are providing those cables.

I'm jumping onto this thread to ask how much these power cables (6 pin, 8 pin, 4 pin molex) can actually provide? I was under the impression that it was 75w for 6 pin and 150 for 8 pin, but judging by the accessories for the card, it isn't :S
 
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