according wikipedia BM1680 was maid 28nm.
https://en.wikichip.org/wiki/bitmain/sophon/bm1680B3 have 4 chips each hash boards,total 12 chips
about 2TFlops speeds of one chip,total 24TFlops.

Today, bminer can make 1300H with 1080ti,its 11.3TFlops,so about 120H per 1TFlops.
If B3 can make same rate, it can make 2800H per units.
But i think it can not be,too weak for hash DDR4