The NES (and most early consoles) ran at 50/60fps, not 25/30fps. It achieved this by ignoring the PAL/NTSC spec and sending all the fields at the same polarity

The NES (and most early consoles) ran at 50/60fps, not 25/30fps. It achieved this by ignoring the PAL/NTSC spec and sending all the fields at the same polarity instead of alternating odd/even fields. This halves the resolution but gives you double framerate progressive scan video, which is a good tradeoff for games.