Hi, I found this (https://annarbor.craigslist.org/sop/d/ann-arbor-evga-gtx-970-sc-gaming-acx-20/6922183544.html) GPU on my local craigslist, and was wondering if it needed a external power connector, or could just run off the 75 watt PCIe rail, its a low-wattage proprietary PSU, Thanks!