http://rhombus-tech.net/riscv/shakti/m_class/ramanalysis/
also added a section analysing options for DRAM. unsurprisingly the top contender is DDR3/DDR3L/LPDDR3. in 3-8 years time it might be DDR4/LPDDR4 but the *massive* speed (1200mhz) is completely insane to contemplate right now. and availability is.... yyeahhh....
l.