dual display for Punch-Out! on Pi5

[dcaputi]

I'm using a Pi5 with RetroPie full 64-bit installer (bookworm) version, and I can't seem to get Punch-Out! to use both displays when launched from EmulationStation/RetroArch using latest lr-mame (0.275).

I was able to get it working in standalone mame simply with numscreens 2 in mame.ini. But with that setup, I launch from ES and only see the main screen.

One hint is the mame OSD menu doesn't show - possibly going to the "other" screen?

So, quick "sanity check" ... should this work? I understand this is an unusual arcade setup but this game is one of my favorites and I have the 2 screens mostly working!

[mikejkelley]

Idk if this will help but it's how I got dual display to work on my countercade... you'll need to SSH in.

14. Stream Retro Games from your Countercade
    If you have a Raspberry Pi 5, you have 2 HDMI outs. That means you can pipe the second signal to another monitor and/or capture card and stream retro gaming goodness! First we'll have to configure dual displays and make sure it takes effect at boot.

Make sure everything is up-to-date:

sudo apt update && sudo apt upgrade -y
sudo rpi-update
Next:
sudo nano /boot/firmware/config.txt
Add the following lines after [all]:

hdmi_force_hotplug:0=1
hdmi_force_hotplug:1=1
hdmi_drive:0=2
hdmi_drive:1=2
hdmi_group:0=2
hdmi_mode:0=82
hdmi_group:1=2
hdmi_mode:1=82

Save the file and exit.
Install xrandr:
sudo apt install x11-xserver-utils
and:

sudo apt update
sudo apt install xserver-xorg xinit x11-xserver-utils
Create the .xinitrc file:
nano ~/.xinitrc
Add the following to duplicate displays:
xrandr --output HDMI-1 --auto --output HDMI-2 --auto --same-as HDMI-1
exec emulationstation
Make it executable:
chmod +x ~/.xinitrc

Currently, you won't be able to xrandr or start it manually with the startx command. This is because only console users are allowed the X server. Let's change all that.
Create the following:
sudo nano /etc/X11/Xwrapper.config
And add the following lines to the file:

allowed_users=anybody
needs_root_rights=yes
Save and exit and reboot.
Now to make sure dual displays are available at boot, edit the Autostart Script:
sudo nano /opt/retropie/configs/all/autostart.sh
Modify the Script: Replace the existing content (usually emulationstation) with:
startx
Save and exit and reboot.

That's it! You should now have duplicate (mirrored) displays!