I have 580 Nitros 8GB Hynix in my rig and I used a timing strap from a 480 4GB hynix card which was much more aggressive. It also worked very well in my 580 Giga Gaming 8GB hynix cards too.

777000000000000022AA1C00B56A6D46C0551017BE8E060C006AE6000C081420EA8900AB0300000 01B162C31C0313F17

I've pasted it above if you want to try it or see if maybe you already have it on (as it is floating around the net everywhere as the best hynix strap to use (if you want to google it if you don't trust me))
Only use if 400/500 series cards with Hynix type memory and only ever change the top two fields (2:2000-2:2250 or your card's equiv) to avoid any possibility of bricking your card.

Also, make sure you are using the AMD blockchain drivers. They make a huge difference for the 400/500 series cards.