I think you might have it wrong, isn't the "17-20G" a 200 Series Card?
This firmware if the Device ID 0x67DF which is the "11260-07-20G" SKU or "Sapphire RX 480 Nitro+ OC 8GB" I'm not sure what card the "01-20G OC" is.
Can you upload the stock firmware for your card?
here ya go models i have :
11260-01-20G
VGA PCIE16 RX 480 8GB GDDR5/NITRO+OC 11260-01-20G SAPPHIRE
AMD Radeon RX 480 | 8192 MB | 256 bit | PCIE 3.0 16x | GDDR5 | Memory clock 2000 MHz | GPU clock 1208 MHz | GPU boost clock 1342 MHz
https://www.dropbox.com/s/2uipzelt3gxo3bx/RX%20480%208GB%20GDDR5NITRO%2BOC%2011260-01-20G%20SAPPHIRE-stock.rom?dl=0
p.s. for Eth i was using this one , performing well and match the revisions
https://forum.ethereum.org/discussion/9650/sapphire-rx-480-nitro-oc-8gb-11260-01-20g-modded-bios-29-mh-downvolt
Cool, is this ROM the silent or oc version?
Cause this card should have dual bios setup.
The rom files say the Core Clock and the Memory Clock + Millivolts for Core and the Timing Hash (Last 6 Digits)