[dragontamer]

Some guy on Reddit claiming to be an AMD engineer was telling me a year or so ago that RDNA took up 30% more area per FLOP than GCN / CDNA.

That's basically the reason for the split. Video game shaders need the latency improvements from RDNA (particularly the cache, but also the pipeline level latency improvements, each clock an instruction completed rather than once every 4 clocks like GCN).

But supercomputers care more about bandwidth. The once every 4 clocks on GCN/CDNA is far denser and more power efficient.