Proof of work update

[Cafevoodoo]

@igno.peverell

Why not ProgPOW instead of Equihash? For 2 main reasons: 1) Equihash remains a lot simpler 2) ProgPOW places an additional burden on proof-of-work verification making it less suited to light environments (cell phones, small VPCs, etc).

@igno.peverell

Equihash parameters are set to use around 7GB of memory, likely parameters are (108, 3). To avoid confusion with other parameters, we will refer to this as Equigrin.

What GPU miner is actively seeking a way to mine on a cell phone? Furthermore, what cell phone can mine Equihash, let alone a 7GB Equihash?