I have had my R9280x black edition for almost a year and i have only had this issue twice. First when I got it and once about a week ago. Ussually I would just solve it by unplugging the card from the Power supply then re plugging it back in but that fix has just recently stopped working. Of course after about an hour or two of gaming the computer shuts off to prevent overheating or damaging the card.
I have an CX750M corsair power supply so there should be no issue with that.
I have an CX750M corsair power supply so there should be no issue with that.