@darksavior said in What Exactly is the Raspeberry Pi 400?:

@Jiryn I use a flirc case for my pi4 but it's not enough so I attached a fan. It's stable just don't go beyond 2Ghz.

Same goes for my fanless aluminium Argon Neo case. I like its magnetic cover that can be easily removed to access the Pi's internal ports.

@lostless said in RPi4 USB ports guide:

@gordonfreemanjr Ignore what the controller is showing on its LED face.

I agree. My bluetooth Wii U Pro clone gamepads also only light the first player LED even if they are working fine for different players in Retropie.

Back-up your ROMs/BIOS/Configs via file shares from you exiting Pi 3 installation - see https://retropie.org.uk/docs/Updating-RetroPie/#making-a-backup-option-2, then install/flash the new Pi 4 image on the SD card. After installation restore the files you backed up in the previous step using file shares to the same locations (BIOS/ROMS/configs).

It's always advisable to make a backup of your existing installation, but you already did this,