They use GD6, which is only half bandwidth compare to GD6X on 3080 3090. Maybe "Infinity cache" could helps in games, but not very useful for memory hunger application like mining ETH.
It's not clear if infinity cache will help compute performance or just CPU to GPU bandwidth which isn't a concern
for mining.
Cache will be interesting for RandomX...this might rival top CPUs for randomx...128mb can feed 64 cores so even if each core can compute less than a CPU you have 4x cores per GPU.
For ETH it comes down to which GDDR6 chips they are using...seems like they are using a 256bit bus so won't be much faster than a 5700 if they are same chips. Bandwidth is about 10% more than 5700 stock settings, so with timings and OC might be able to hit 65-70, and with higher core count id say 70+ is doable at the same power of a 5700.
I bet 5700s will come down to under $300 once these launch though so they will still be better in terms of $/hash.
I doubt it will perform like a mid range CPU. Random-X is not only about cache, it's designed to perform on CPUs and nothing else.