Power supply problem 6pin > 8pin

Solution
6pin delivers 75W, 8pin delivers 150W, PCI-E slot delivers 75W, so the GPU itself requires 300W, this is a pretty huge leap by gigabyte considering the chip that comes from nvidia is rated at 140W altogether. That's why I suggest getting a 960 version which requires just one 6pin, else you have to buy a new psu which will increase the price and I guess you are on a budget.
6pin delivers 75W, 8pin delivers 150W, PCI-E slot delivers 75W, so the GPU itself requires 300W, this is a pretty huge leap by gigabyte considering the chip that comes from nvidia is rated at 140W altogether. That's why I suggest getting a 960 version which requires just one 6pin, else you have to buy a new psu which will increase the price and I guess you are on a budget.
 
Solution


The Graphics Card should have an adapter that combines 2 molex connectors to a 8-pin connector for that purpose inside the package.