PSU Wattage & GPU usage help

[Modzau]

Hey guys so I have a old power supply running 3, 12v rails however it only consists of 2 six pin connectors. I want to put in a 970 xtreme which requires 2 eight pins, however I have 2 six to eight pin connectors, so I was wondering if its fine to overdraw 22.5 watts each 6 pin connector. 

 

"The original 6 pin, 75 watt specification was for a minimum current of 2.08 amps for each +12 volt line, hence 75 watts.

3 +12 volt lines x 2.08 amps each = 75 watts.

However, The 6 pin PCI-e power connector is actually capable of handling more than 75 watts.

3 +12 volt wires x 4.16 amps each = 150 watts maximum wattage.

The two black ground wires were added to handle the increased current."

 

I read this and was just wondering if I would blow up my house or something, or it would be stable. 

Any help is much appreciated thanks!!!
 

[TheRandomness]

It'd be a better idea to:

A: Get an RX 480 (4 or 8GB is fine) or GTX 1060 (6GB please) instead, both should be cheaper and both perform better.

B: If your PSU is like that, please get a newer, better one, like a CX450M. 

[Modzau]

The thing is I own the GPU because it was given to me, and a newer PSU is another $60 I really don't want to spend more money, I just want to know will it work and not kill everything?

[mariushm]

The number of rails is irrelevant, the total amount of watts that can be provided on those 3 rails is. On most power supplies that have multiple rails, each rail by itself can provide up to some amount of watts, but when all three rails are used at the same time, the total amount is less than if you'd simply add the watts of those 3 rails.

For example, on a very good 550w power supply you may see 3 rails each with 18 amps (12v x 18a = ~ 215w) , but overall just 45a are available on 12v (or 540w), not 3x18a= 54a which would equal to 648w.

 

If the power supply is good, on a power supply with three 12v rails, one of the rail is usually reserved just for cpu power connectors,  one may be used for 24 pin atx connector and molex and sata and maybe one pci-e 6 pin connector and the third rail may be the other pci-e 6 pin connector and some sata and molex connectors.  Others put both 6 pci-e connectors on a separate rail.

 

A standard 970 card idles at around 9 watts and goes to about 179 watts in some heavy benchmarks, not in all games. Your video card, even if it uses let's say 200 watts, should still be able to get enough power from your power supply, unless it's really a dud.

The card will pull about 50-60 watts from the pci-e slot, so from the 24 pin atx connector, and the rest of about 100-120 watts will be pulled from the 8 pin connectors.

The video card would have probably been fine with just one 8 pin connector (allowing up to 150w from connector and 60w from slot, so 210 watts in total) but my guess is the manufacturer wanted to have some more power available in case user wants to do heavy overclocking, so in able to do that they put a second pci-e power connector on the card. They could have made it with a second 6 pin connector, but probably they made it with two 8 pin connectors because it was cheaper to buy 8 pin connectors in volume, or because it was more visually pleasing to have 2  8 pin connectors, or maybe because they wanted the card to look more badass.

 

As one pci-e 6 pin connected is rated for 75 watts (but can be perfectly capable of more than 100w), it would be perfectly safe to use a 6pin to 8pin adapters to power the card, two 6 pin connectors will be perfectly capable to give the card 100-120w it would take from those connectors.

 

But all of the above is only valid if the power supply is good. With a brand name power supply, you can look at the power supply label and check the total watts on the 12v rails.

 

If you can't figure it out, take a picture or say the complete brand and model number and i can tell you for sure if it can handle your card.

[Mick Naughty]

If the system handles load over time then it works. 

[Modzau]

Thank you all so much for the  help all!