@mitu Thanks that worked perfectly!

Oh ok I fixed it I just had to reset the keyboard

i discovered (trying) that autoconfiguration doesn't work for single emulators, like psx. so i read some internet guides.
i configured it manually, editing the file /opt/retropie/configs/psx/retroarch.cfg
adding this:

input_player1_joypad_index = 0
input_player1_b_btn = "k"
input_player1_a_btn = "m"
input_player1_y_btn = "i"
input_player1_x_btn = "j"
input_player1_l_btn = "n"
input_player1_r_btn = "m"

and this works. but i would like to use other buttons (the ones upper-right of this keyboard: https://www.google.com/search?num=20&newwindow=1&sa=G&hl=it&q=mini+wireless+keyboard+h9+2016&tbm=isch&tbs=simg:CAQSlwEJsBCE-pIGGwQaiwELEKjU2AQaBAgVCAAMCxCwjKcIGmIKYAgDEiixBoICpga6BrQGhxKgDLUGsAaGArwhqz2sPZ80wT23PbI94DaVNKI9GjBj7Kiy8UuBZo8x1oDaiZnH_1SIW4APyyJA5zG_1e3DOfb2yla_1PcHcPwD-Jzh0XPxiYgBAwLEI6u_1ggaCgoICAESBDolrPEM&ved=0ahUKEwjmoL-xr-LbAhWDiCwKHaiACOAQwg4IJSgA&biw=1360&bih=631#imgrc=kZkd0BQ1qYUw-M: )
how can i do?

@deltax5 you can build RetroPie on top of Linux. Check out the official documents for more info on doing that. I've got a little laptop running Ubuntu and it's pretty good. If you put RetroPie on top of that I think you'll be onto a winner. Pi3 is still not great for N64 emulation.