Interesting. The article only mentions "The eDRAM also required 1/5 of the keep-alive power compared with an SRAM device." Could you explain more about eDRAM's constant refresh and is that something that would be fixed someday, do you think?
The DRAM will leak charge without a refresh, which requires power frequently every second. SRAM doesn't. Maybe SRAM doesn't sleep well enough anymore to conserve standby continuous power? What happened to near-threshold operation?
Refresh seems to consume about 0.5W. The L4 latency is about half that of DDR channels, and the bandwidth about the same as 4 DDR4. Typical hit rate 95% (that would be remarkably good in general, but maybe the gamer market is what they aim at where locality might be better).
Not clear this is better than a Memory Cube. But probably much cheaper.