If your CPU has integrated graphics like intel HD or something similar, remove the GPU and use the display port on your motherboard, if you don't see that artifacting then it's probably the GPU
you should prolly return it rather than messing with it's voltages as this dude above said
it's more likely to be your GPU that's the problem because i've never seen such a severe case of artifacting
If you're overclocking it, turn down the overclock a bit, if you aren't, then try downclocking it a bit, if that still doesn't work, try increasing voltage, checking connections, etc...
Otherwise it might be defective.