I recently upgraded from a GTX 1060 to the RX 5700. I have two monitors, one plugged into the 5700 and one plugged into the motherboard (Intel graphics). With the nVidia card, I could be doing or playing anything on the monitor plugged into the motherboard and it would have no affect on what I was doing on the monitor plugged into the nVidia card.
With the RX 5700, anything on the second monitor does affect my framerate (or maybe even just the Freesync rate) where games are close to unplayable.
The nVidia software did support the Freesync on my monitor.
Is there a setting I have missed in the Radeon software, maybe in Windows or somewhere else?
I also have the secondary monitor connected the to the iGPU but don't experience low framerates. What framerates are the games running at? Can you check at what Hz the primary monitor is running at during gaming? I generally only have monitoring software and discord opened on the secondary monitor during games though.
Probably won't make any difference but try to set the games as high performance in Display Settings - Graphics settings. Browse for the games and set as high performance. Windows should show you that the Power Saving GPU is the iGPU and the High Performance GPU is the Radeon.
Post your specs including the monitor.
The primary monitor runs at 144Hz unless freesync changes it. I set the high performance settings you mentioned and it didn't do anything. I'll just use Rocket League for my example and testing. Launching the game with no playing video on the second monitor I get 150-200 FPS in game and the monitor shows a constant 144Hz. If I then play a video on the second monitor, the FPS in game doesn't seem to change but the monitor is now wildly changing from it's refresh. It's hard to tell because it's changing so fast but looks like it's ranging from 30Hz to around a max of 90-100Hz.
Games are running on a 1TB M.2 drive
Monitor 1: Aorus AD27QD 27" 144Hz 1440P FreeSync
Monitor 2: Acer 23" 60Hz 1080P
Radeon driver: 19.9.2
Update: Turning Freesync off completely makes the issue go away. I can do anything on the second monitor and the primary monitor stays at 144Hz and the games continue to run smoothly. So it definitely appears to be something related to Freesync.
I played a game of RL on my main 144Hz Freesync monitor with a Youtube video in fullscreen on the secondary 60Hz monitor. No issues. Same smooth gameplay. The monitor refresh rate was mostly sticking to 144Hz. It was not going down to 30Hz.
Using 19.7.5 driver, hardware acceleration disabled in Firefox. What is the freesync range of the monitor? Did you change anything using CRU?
Radeon software reports 48-144Hz Freesync range. I'm not sure what CRU means. Firefox is set to Recommended performance which I'm sure has hardware acceleration on. The same as it was when all worked fine with the nvidia card.
Tried with hardware acceleration on. Works fine. Strange that it goes down to 30Hz. Download Custom Resolution Utility and check from there. Select the 144Hz display and click on edit. Check the v rate. In the game are you checking the FPS with something? Also when you are playing the video on the secondary monitor, how does the primary monitor behave in desktop? Does the mouse feel '144Hz smooth' and does the refresh rate stick to 144Hz or is it fluctuating?
I had experience in the past, where having rainmeter or foobar2000 playing on the second monitor, the primary monitor's refresh rate would constantly fluctuate all over the place and even moving the mouse on the desktop did not feel smooth but I don't think it ever affected a game. Could be the driver version.