Pi 4: Is there any performance penalty to running a second screen?

[bomblord]

Note: I'm not referring to 2 4k screens which requires a drop to 30hz on each.

I have 2 screens a 1080p TV and a small 7" screen that's not quite 720p. I have some ideas that I'm thinking of where I run emulators on the big screen and do something simple on the second screen like display some information. Maybe box-art, maybe system load, maybe something else entirely. With many emulators pushing the limits of the Pi 4 I wanted to be sure there wouldn't be any performance degradation from running both at the same time.

[jamesh]

The main penalty with be SD Ram bandwidth I suspect. Grabbing the data for two full 4K displays from memory and stuffing it out at 30Hz is a huge hit on that. Whether that will be noticeable in your use case is difficult to tell. However, running one display at a lower resolution will help a lot.

There's also a general CPU and GPU hit in dealing with much larger bitmaps (the desktop), you have four times as much data to throw around.

AH: Just reread your post. Those displays will be fine.

[PeterO]

AH: Just reread your post. Those displays will be fine.

There's me shouting at the screen "You've not read the OP's post carefully enough "
PeterO

[bomblord]

The main penalty with be SD Ram bandwidth I suspect. Grabbing the data for two full 4K displays from memory and stuffing it out at 30Hz is a huge hit on that. Whether that will be noticeable in your use case is difficult to tell. However, running one display at a lower resolution will help a lot.

There's also a general CPU and GPU hit in dealing with much larger bitmaps (the desktop), you have four times as much data to throw around.

AH: Just reread your post. Those displays will be fine.

Good to know, thank you!