@mammoth you connect another controller and start playing?! In arcade games you may need to insert two coins and both players have to press start to enter the game.

@Zing Excellent, thank you very much!

I leave the information here if somebody has the same issue:

FIXED turning off 'service mode' on 'dip switches' from the mame menu in that screen.

Next time I'll give more information, sorry!

@voljega Great discover ! That's also a nice way to explain the meaning of parent/clone roms 🙂

There's no edit function... (lol just found it making this - duh!)

Added psx.videomode=CEA 4 HDMI to the recalbox config

changed boot\config.txt

###Aspect ratio
sdtv_aspect=1 # 4:3
#sdtv_aspect=2 # 14:9
#sdtv_aspect=3 # 16:9

to
###Aspect ratio
#sdtv_aspect=1 # 4:3
#sdtv_aspect=2 # 14:9
sdtv_aspect=3 # 16:9

and now the psx works, doesn't fill the screen anymore but it is central which is nice, still can't get the N64 screen central