I have a Lenovo Z51-70 80K6 with an i7 5500U @2,4 ghz and Intel HD Graphics 5500. I connected my laptop to a 4k TV via HDMI and when I try to play games in fullscreen,the refresh rate goes down(I play the games at 1080p),and it's unplayable.If I play the game in windowed mode,it workes fine,but I want it in fullscreen.When the laptop isn't connected to the TV,it works fine,although my laptop screen has only 60HZ refresh rate. Is it a problem of my iGpu or a problem of my laptop?
I understand that you are having a refresh rate drop when you are playing games at full screen, I apologize for any inconvenience.
Regarding this, I was checking and this unit supports 3840x2160 @60Hz only while using display port. When using an HDMI the max. resolution is 2560x1600@60Hz. This means that the refresh rate drop is happening there.
If possible, I would recommend you to use display port. If not then it needs to be a lower resolution if you want higher refresh rate. Also, if this does not solve your question, To better assist you with your request, I will need to check some information about your computer. Please follow these steps:
1. In the keyboard, press WinLogo key + R.
2. In the Run box please type dxdiag and hit Enter.
3. Click on Save All Information (save it in your desktop).
4. Attach the report to this thread.