You can either use the Polaris one-click timing patch feature or you can download an original/stock rx470 Samsung bios and edit it manually. It's pretty easy as there are already numerous tutorials out there that teach you how to do it step-by-step.

Here is a link to a PBE one-click patch tutorial: https://forum.getpimp.org/topic/1530/bios-modding-with-polarisbioseditor-one-click-timing-patch-on-windows
Good luck.