Gamers Nexus has a piece discussing why AMD went with HBM2 memory instead of GDDR5, despite it being about 3x more expensive: while bad for profitability, the company couldn’t have reasonably gotten GDDR5 onto Vega’s present design without severe drawbacks elsewhere. It wouldn’t compete, and we’d be looking at another Polaris mid-range GPU or much higher power consumption.



At less than 30W for 16GB of HBM2, GDDR5 just can’t compete with that power consumption under command of the Vega architecture. It’d be cheaper to make, but would require significantly higher power consumption or a smaller bus, neither of which is palatable. AMD isn’t using HBM2 to try and be the “good guy” by pushing technology; the company was in a tough spot, and had to call riskier shots out of necessity. Although it’d be nice if every GPU used HBM2, as it is objectively superior in bandwidth-per-watt, both AMD’s architecture and market position pressure the company into HBM adoption.

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Source: [H]ardOCP – The Cost of HBM2 vs. GDDR5 Memory