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It is best to save the origial BIOS from your cards and modify the memory straps yourself and then reflash and test than to flash some BIOS that you download that might not be Ok for the exact model of your cards or they may not hold up the set frequencies/timings for example.

Hey mate
So I've made my first 2 mining rigs, i replicated what you built here, I can get 29 mhs per card, I'm having trouble with the core voltage.

I've tried wattman, afterburner, bios flash but the voltage is always unchanged in gpuz and watts from the wall remain the same.

What are you using to drop the voltage?
Thanks.