Got a RX570 nitro+ 4GB some days ago. Strange - has the same VRAM-Types - one Elpidas and one Hynix like RX580.But Hynix, instead of the RX580 Pulse 4GB, has the Hynix as the main VRAM relevant for tuning. I optimized successfully the BIOS by trying several straps - found the right one at the end. Got 29.8 MH/s - quite good, but only with the Glaymore miner under W10 and BIOS parameters: 1150GPU/2060Mem/0.9V Mem/0.86GPU. Power consumption @90-100W. With Ethos-OS I got only 26.5MH/s - anybody an idea why? If any questions - just ask for.