This is specific to the SX-1 FPGA. I've just gotten one and trying to understand the options. For instance, there is a DIP switch to change between 2MB and 4MB mapper. I've searched around and found no explanation why the 2MB setting would ever be preferred over the 4MB setting. I assume both were available in cartridge form since the 2MB was probably first and remained a less expensive option, but I'm not sure of the importance of it on the SX-1 since 4MB is also standard. Do some utilities only support 2MB mapper? Thanks!
I did find it interesting that one game, Alien2.rom, loaded with the MegaRAM 8kb bank, but not the 16kb bank...oh to understand. 
