Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
S
My bad ...
I had to activate multitap in retroarch. It's explained here : https://github.com/RetroPie/RetroPie-Setup/wiki/Playstation-1#multitap-3-8-player
Works great now !