"128 Mbit was quite popular"
Back in the old days, each new generation meant 4 times the capacity of the old Sometimes they would produce a 2x one, but that was usually after the introduction of the 4x ones. To be honest, it's been a few years since I followed the DRAM industry much, so I don't know what current trends are...
An example was the 128k DRAMs were actually two packaged 64k DIPs stacked on top of each other. IBM bought a whole flock of these to put into the original PCs. They never did produce a 128k die. At least none of the major manufacturers did, they just went from 64k to 256k.
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