Tonga is really not optimized
Tonga it's the problem, by itself...
It was close to be a scam, from amd...
They said Tonga was going to replace the aged Tahiti.... but they were just kiddin'
Tonga is more efficient for gaming, it has better memory efficiency, and perhaps more efficient GPU? My memory is cloudy. Anyway, for mining it isn't as good, improvements are for gaming.