I've stumbled upon some post on timings editing and decided to tinker a little with my cards. I have Gigabyte RX480 4Gb G1, Sapphire RX470 Nitro 4Gb and MSI RX460 OC 2Gb. All my cards have Hynix memory, H5GC4H24AJR.
I took the timings from PBE (UberMix 3.x AFAIK), which PBE offered for my cards and done some improvements onto it. Gigabyte cards wouldn't work good with it, HWinfo reported thousands of errors even at 2000MHz. But Sapphire and MSI received noticeable boost in hashrate: from 30.1 to 30.5MH for RX470s, and from 13.2 to 14MH for RX460s, with same clocks as before timings modification.
Here's the strap from one of my RX470s (>1500): 777000000000000022339D00CE515A3D8055111230CB440900400600740114206A8900A00200312 0100F292F94273116
This one is from RX460 2Gb (>1425): 777000000000000022339D00CE515A3B805511112FCBD408004006006C0014206A8900A00200312 0100F272D8D263015
If those straps work good for you, please let me know. Also won't mind to receive some ETH as thanks
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