Super Mario Bros runs slow on lr-quicknes

[TheHighlander]

I'm running RetroPie 4.3 on a Raspberry Pi 3 using an official Raspberry 2.5A power supply.

I'm comparing the speed it's running at to a European NES (PAL) system using the regular Super Mario Bros/Duck Hunt cartridge. I've noticed that the emulated version runs a lot slower on the whole (music sounds slower and the game plays slower).

Most issues I find are about games running too fast. I'm convinced the Pi can handle the speed but I'm not sure what's causing the slow down?

Am I just using the wrong ROM (i.e. a 60Hz rom on a 50Hz system)? Or is there a setting I can change?

Thanks!

[TheHighlander]

Yeah...that was it. All my ROMS were NTSC roms. A PAL rom runs a lot quicker.

[mitu]

I wonder how quickness determines the region - there's nothing in the Core Options (like Nestopia or Fceumm) which can select the Region. How is the ROM file named ?