The bitcoin mining edge that AMD cards had over Nvidia cards was came down to the AMD ISA having a single cycle hardware rotate instruction, which the NVIDIA cards lacked. Also the AMD philosophy of many dumb cores vs the Nvidia's philosophy of fewer smarter cores made a significant difference.
This is equivalent to the SHA-256 Ch "Choose" function.
It also can be used to compose the SHA-256 Maj "Majority" function with an additional XOR.
Additionally, the AMD ISA doesn't have a "rotate" instruction per-se, BFI_INT is "bitfield insert", which can be used to compose arbitrary length rotates, but is not strictly a rotate in and of itself.
AMD ISA also has instructions for computing integer add with carry, which is great for crushing elliptic curves.
NVidia really, really, sucks for integer compute. Friends don't let friends buy NVidia!
