One cool and useful item that came with my NEC PC-6001 is this RAM/ROM expansion cartridge. It plugs into the side of the 6001 and doubles the memory to 32KB, and it also has two ZIF sockets for ROM expansion.
At this point, I’m not sure what can be done with the ROM expansion but I hope to find out more someday. As for the RAM, many tape games require it, so it seems like something of a must-have expansion for this system.
The ZIF slots for ROM chips basically lets you really easily make up your own cartridges. You just need to program a PROM (modern EEPROMs can be programmed easily with a cheap Arduino setup), drop it into the socket, flip the lever to lock it in, and bingo! you have a custom cartridge. This sounds really handy to me. Though of course I suppose you could just buy any old cartridge, desolder the ROM chip(s), solder in a ZIF socket, and get basically the same thing, which I may well end up doing for my PC-6001.
Aha! That makes a lot of sense. I suppose whatever ROMs you might put into the ZIF sockets, it’s essentially a cartridge, anyway. Thanks for the insight!