Someone asked this question in another thead, and I gave what I thought was a good answer, but I don't really KNOW the answer to this. I've never talked to anyone who claimed to know or read or seen it anywhere. Maybe someone with know how as to how the NES worked can help?

Why was it needed to hold down the Reset button before turning Power off on the NES with the first generation of battery back up games?

My theory was due to the power current. If you just hit Power, it sent a surge of eletricity through the system, the same way that computers do when starting or shutting down, and when the NES starts up. With the early batteries, there was a danger of that surge damaging save data. But if you hit Reset first, there's no surge of power, and then while holding it in that 'reset' mode you could then cut the power off and be safe.

Later NES battery games were better protected, I guess, or better designed, so no problem with that. Sega did'nt have a problem with it with their battery games either, so it's really a weird problem.