I wan to thank you all for the great help, I would never ever come up with this solution on my own.
I hope I can pay back the favour once I get more experience.
Great community!
Thank you for saying a big thanks to all those who makes a contribution to your problem and I'm glad you are able to solve the problem too, I have 10 pieces of gt1660 super and they are all running on hynix memory, out of the box I get 30-31MHs without any bios modding or flash, it's definitely the memory downclocking thing