Atari800 support ??? Excellent !!! At last !!! Congratulations !!!
The iconic 80's retrosystem in USA and Latin America (together with c64 and MSX)
Thank you !!!

My settings for Rpi400, with no problems:

over_voltage=6
arm_freq=2147
gpu_freq=750

Y have 1Tb external HDD with 3 partitions to test in parallel Batocera, Recalbox and Retropie, this 3 partitions are equally divided in NTFS format each one and identical romset in each one. First partition is labeled BSHARE (dedicated to Batocera), second partition is labeled RSHARE (dedicated to Recalbox) and third partition is labeled PSHARE (dedicated to Retropie). And three microSD cards with this 3 different systems. In the menu of each system is possible to select the corresponding partition to use by each system (but Retropie is a little more complex). So, your idea it's perfectly possible.

Answered:

https://forum.recalbox.com/topic/22567/problème-bouton-on-rasperry-pi400

Some Pi400 features not yet supported (like power on/off or overclockin) I'm waiting full support too and above all: Vulkan support. (But this is a mission of Raspberry Development Team and Retroarch Development Team, after this, Recalbox Development Team can update to Vulkan support, there is still a long time for this arrival)

Debes hacerlo en el archivo config.txt que está en la primera partición de la tarjeta. Así la Raspberry Pi sabrá la configuración correcta desde el booteo.

Aquí está toda la documentación respecto a la configuración de video del archivo config.txt

https://www.raspberrypi.org/documentation/configuration/config-txt/video.md

Esa partición se ve desde windows, asi que puedes insertar la tarjeta en el PC y hacer la configuración con el Bloc de notas.

Recuerda respaldar el config.txt original, para reponerlo si te equivocas en algo.

Même problème ici, ne fonctionne pas sur Raspberry Pi 400

I am veteran too. You stop emulationstation through SSH with "/etc/init.d/S31emulationstation stop" before remove roms? Remember that gamelist structure is remaining in memory so, you need to unload emulation station from memory before delete roms or edit gamelist.

I have same problem. I copied from "/recalbox/share_init/system/.emulationstation/es_systems.cfg" to "/recalbox/share/system/.emulationstation/es_systems.cfg" and modified the copied file, deleting extensions that I wan't to see (in x68000 I only want to see m3u files). I reset, but doesn't work, I still viewing various dim files and corresponding m3u files in the game list. It's right my procedure, or I'm wrong in some step?

Same problem, impossible to reproduce, very random behavior, but I have noticed, in my case, that in more frequent when a romset is scraped with Skraper program, then some not detected games are scraped with Recalbox internal scraper. Maybe some inconsistency due two (or maybe more) tools when scraping, causes this problem.

Reported from Raspberry Pi 3b+ and Raspberry Pi 400

Hi!

I'm creating "m3u" files to group "dim" mutidisk games for X68000 System. The maximum number of "dim" files per "m3u" is two? Because i'm trying to run "Aquales" game (3 disks, exclusive and hidden gem of X68000), and doesn't work (I change disk index with Hotkey+B, but doesn't work).

I found this:

https://laptopified.com/mini-pc/best-mini-pc-for-emulation/