Updated: Nov 24, 2020
We are in the era of 7nm chip. Till now it is the most efficient chip used in GPU. Before we had 14 nm chip. Sapphire RX 580 8 GB is 14nm chip based on Polaris architecture launched in 2017. I have used these cards for mining and after proper tuning I could get max 31 mh/s at 80 watts on Ethash algorithm. Then came the first 7nm chip GPU, Radeon VII based on Vega architecture in 2019. It is the top end segment card from AMD. Radeon VII card is the most efficient cards from AMD for mining till now. This card was in huge demand during its initial release and got sold immediately.
Now it's time for AMD RDNA2. It is the renewed architecture of AMD RDNA RX5700 XT GPU. This card will surely outperform all. For long time NVIDIA ruled in the top end segment of GPU performance. This card will outperform NVIDIA's top end cards. AMD is launching three cards based on RDNA 2 architecture. These are the Radeon RX 6900 XT, 6800 XT, and 6800 respectively. With these latest cards, AMD is aiming squarely at NVIDIA’s recently-launched GeForce RTX 30-series line up, aiming to meet (or beat) the RTX 3090, 3080, and 3070 respectively.
AMD claims the performance boost for RDNA2 will be 50 % more than its predecessor RDNA RX 5700 XT. With proper tuning RX 5700 XT can achieve 51.5 mh/s at 140 watts on Ethash algorithm. Now if you look at the comparison chart above RX 6800 XT has computational units CU almost double than RX 5700XT. So based on this we can predict RX 6800 XT can achieve 80-100 mh/s at 150- 200 watts.
This card will will be in huge demand as it will be the most efficient Ethash mining GPU. Also 4 GB cards, both ASIC and GPU won't be able to mine ethereum on Ethash algorithm as DAG size will increase more than 4 GB on 26th December 2020.
The card has been scheduled to launch on 18th Nov but in India I think it will be available no sooner than first week of December. Never buy from Amazon as prices will be insane. Get it from your local reseller. I will be getting one for myself. I will get my hands dirty on it and post update on its performance. I will be adding this card if I manage to get one to my present running mining rig with 4 Sapphire nitro RX 580 8 gb gpu. It will be a mixed GPU mining rig.
If you have desire but never tried mining before then this is the right time to get into.