My guess this happens because you specifically set the resolution somewhere - either in /boot/config.txt, or in each individual RetroArch core. EmulationStation and emulators (including RetroArch) should pick up the current resolution and run in fullscreen, without the need to set the resolution.

WOW! That is fabulous! Thanks for the link!

If you are set on using a big CRT. You gotta make the cabinet very strong. I'd suggest 3/4 MDF or Pine hardboard.

@ikarampa Is is a post that's 13 months old, opened for PPSSPP on a Raspberry Pi. You might have better results posting on the LibreElec forums to ask for advice.

@tostati you can still set Kodi to 1080p btw whilst using 720p for everything else. Kodi on RetroPie restores the previous video mode on exit. I use 720p but boot to Kodi which switches to 1080p. Then I exit to es, and have 720p again.

so ,i was kinda overloaded with stuff didn't realy proceed with what i posted, i am back to making the arcade now ,still i am fazed with this problem ,since i am gonna be making a shutdown/boot button for the pi,if i connect in parrallel to this connection the button that you push to manually open the TV is it gonna work ?.My main concern is frying the pi due to the tv being a higher power device ,should i use a relay for that kind of work?.

@valhalla_pi I personally prefer to force everything into the precise dimensions of the (4:3) viewport: custom aspect, non-integer scaling, plus smoothing to fuzz it up a little. In the rare event that I come across a game that looks distorted, I tweak the settings for just that game.

I use a VIZIO D50u-D1 50-Inch 4K. I picked it up specifically for the low input lag, and it seems to work great. I made sure to use the fastest HDMI port (one is labelled as "best") and turned on game mode, and turned off all post-processing options. rtings.com lists it as having 13.5ms, which is excellent for something that's not a computer monitor. http://www.rtings.com/tv/reviews/vizio/d-series-4k-2016

Ive hooked my pi to multiple different monitors with different resolutions via hdmi through passive dvi converters and the OS always seems to auto fit. Nice thing about the Pi is it's small and portable, take it to the tv and test it before you buy it, i do that at the salvation army shop sometimes when picking out CRT's, haha.

CRT... I watched a fun video on those TVs before... just incase anyone is interested, here it is.