@sugarfree Thanks for the technical clarification!

I noticed some PAL/Europe games have an SBI warning indeed. I am happy with the OOTB experience though.

I wound up imaging a new memory card and just moving my roms, bios & collections over.

What it seems like the prob was, is that when you rotate it back to 0 in the sudo nano /boot/cmdline.txt the screen default resolution wasn't doing the trick. When you go to the settings of raspi-config for screen resolution and set that to default it shifts everything to the left but doesnt stretch it all from left to right. it basically stops at the center of my computer screen.

Anyway I would be nice to figure this out for others..

@romstar said in What's the correct aspect ratio I should be using as a config for a HAPP / VISION PRO 19" LCD arcade monitor for MAME Horizontal / Vertical games:

I changed the bottom line to mame2003_tate_mode = "enabled" which ultimately resolved my issue. now The vertical game is finally displaying the way it should on my HAPP Vision pro monitor mounted vertical !! At some point I'd like to build a vertical only list of games and have the menu / retropi running exclusively in vertical mode.

I knew it would change your life. I would not recommend trying to make the whole of retropie itself work in vertical mode yet, though. I stayed with my rotating monitor because rotating emulationstation causes performance issues. I believe it also became more difficult to rotate emulationstation on the Pi4 because the option was deprecated. I stayed with my Pi3b for my vertical MAME games for that reason and hope that a good solution for a fully vertical system presents itself later.

I solved, resetting to default, and after putting aspect_ratio_index = "21" , and also the rotation, thank you very much for the help I love you haha

I found one! A friend asked me for a seperare Tate-Card to switch to when using his Tate-Display. Simply use the Arcade-Sytem instead of seperate Mame and FBA-Systems. Enter a game with Mame2003-core, activate rotation and save the system configuration file (not game or core override!). Done. The rotation setting will also apply to all FBA-games.