Reddit reviews EVGA Dual 6-Pin Female to 8-Pin Male Cable

you need one of these
https://www.amazon.com/EVGA-6-Pin-Female-8-Pin-Cable/dp/B00M49SELW

or a new power supply.. if its really old.

Running a 2nd monitor (but only gaming on the primary monitor) barely affects power usage.

You would want a 2x6-pin to 1x8-pin: https://www.amazon.com/EVGA-6-Pin-Female-8-Pin-Cable/dp/B00M49SELW

Thats not the right cable.

You need the exact opposite- two 6 pin to one 6+2 pin (8 pin). The one you linked is designed for miners and will risk causing a fire if used improperly.

Edit: something like this (obviously the price is wrong) https://www.amazon.com/gp/aw/d/B00M49SELW

Sometimes cards come with them. Pretty sure my 390 had a few adapters in the box. If it doesn't this is what you need

https://www.amazon.com/gp/aw/d/B00M49SELW/ref=mp_s_a_1_1?qid=1465397655&sr=8-1&pi=SY200_QL40&keywords=dual+6+pin+to+8+pin&dpPl=1&dpID=31Zl92fPY8L&ref=plSrch

https://www.amazon.com/EVGA-6-Pin-Female-8-Pin-Cable/dp/B00M49SELW/ref=sr_1_2?ie=UTF8&qid=1482707240&sr=8-2&keywords=dual+6+pin+to+8+pin

You can get adapters for that. However, it would appear that PSU is a standard ATX PSU instead of a proprietary one, it would probably be smarter to upgrade it to something a little better. The CXm is a decent budget line, but the Focus Gold/Gold+ or SuperNOVA G2/G3/GS lines are better, more expensive options.

I think each of the 8-pin connectors is the equivalent of 2 6-pin connectors. So if they've only given you those two, it really seems as though this power supply was not designed to put out as much power as the card is looking to draw.

But since there are various sources of 12v power coming out of your power supply there may also various ways of adapting them around. Just like you can combine 2 6-pin into an 8-pin, you might have some 2x2 4-pin connectors or 4x1 4-pin connectors (designed for things like additional motherboard power, floppy and HDD and SATA power, etc) that you can adapt into the missing 12v.

Keep in mind that if you do manage to get the 2 8-pin connectors you need, you'll likely be draining every last watt out of your power supply and operating it at 100% output all the time. This will severely shorten its life if it's not a top-notch piece of equipment.

And you're sure the PSU cables don't have an extra 2 pin hanging off? Something like this would work.

https://www.amazon.com/EVGA-6-Pin-Female-8-Pin-Cable/dp/B00M49SELW

Some GPUs come with this included

https://uedata.amazon.com/8-Pin-Dual-6/dp/B00M49SELW/ref=sr_1_12?s=pc&ie=UTF8&qid=1468473290&sr=1-12&keywords=molex+to+8+pin

That's the identical one that shipped with my evga card.

You absolutely can run a GTX 1080 if you were running a GTX 970 before.

This adapter should be all you need.