i think it would be the OVER CURRENT PROTECTION inbuilt in the 570 that underclocks the gpu when it detects applications like furmark.
try this : download latest gpu-z and check the disable OCP. then try to run furmak.
Bad advice, I have already seen a lot of cards already damaged from due to the power vrm phases blue smoking. Do Not Do this!!!!! It can damage your card. Look online and you will see for your selves.