Welcome to tsf. Another possibility is the card is being under powered which also does create artifacting. First make sure you have the latest driver for both the motherboard and the video card. And the latest bios for the motherboard.
If that doesn't do it download speed fan in my sig and post back with the temperatures and voltages it reports. Also post the make , model , and wattage of the psu.
If that doesn't do it download speed fan in my sig and post back with the temperatures and voltages it reports. Also post the make , model , and wattage of the psu.