HBM2 is somewhat meaningless. The whole HBM is bad stems largely from a capacity issue. Fiji having lots of compute, bandwidth, and relatively low capacity.
The impression I get is that in this context it is the diminishing returns versus compute and bandwidth noted for Ethereum in particular for GPUs using HBM and GDDR5X. Both Fury and the GTX 1080 saw reduced rates given their resource advantage over lesser products, whereas the GDDR5-based 1070 saw better results. I haven't seen a definitive analysis as to what caused that outcome, or how significant that difference still is.
The capacity doesn't seem to be strictly a problem, given the popularity of 4GB cards even in the era where Fury was considered something letdown, and Ethereum trying to adjust at various times so that it stays applicable to more GPU hardware.
Vega would have significantly more cache, probably different VGPR arrangement,
I'm not seeing a strong indication that VGPRs are changing that much in terms of what the software sees, how the VGPRs look from the die shot, or how AMD's slide on its SRAM customizations seemed to be more concerned about making the register files just be more efficient in terms of area, power, and delay.
Assuming HBCC is even useful or practical for coin mining with all the risers. Some adjustments would seem necessary.
It may depend on the cryptocurrency or mining algorithm, but outside of possibly secondary effects like better page handling or bandwidth utilization of on-board RAM, HBCC's ability to page large amounts of memory doesn't sound like it should help.
The reason for GPU-friendly cryptocurrencies is that they were adjusted to not be scalable for ASICs or esoteric accumulations of ALU or memory storage that might lead to concentrations of mining capability in specialized hardware or clusters.
The size for Ethereum is aligned with a more general amount of GPU RAM and leans on the specific abundance of local device bandwidth, and odds are if HBCC and its capacity play somehow had an outsized competitive difference they could tweak it further so that it didn't.
, probably last a good 2 months even with high power when difficulty spikes and assuming coin price doesn't go up (it would likely with a difficulty spike) it would half way pay itself off...
