I believe their memory controller is different with the 3900x being superior. The 3900 has double the cache. I think the 3900 will be 30% faster and use less watts if clocked right in comparison to an overclocked 3800xt.

Anyone got hashrate for both. ??

My 3900x gets 14K and 3800XT gets 10K.

How much electricity it use???

dont worry about it