I have ASUS GM501GS i7 CPU with GTX 1070. The display is 144Hz.

By itself, it works fine.

Then I plug in a monitor that runs at 60Hz into the HDMI out. After that both laptop display and the external monitor jump frames.

The laptop is running with GSYNC enabled. I have tried all sorts of things from searching internet. Eg running external monitor on Display mode, changing laptop display from 144Hz to 120Hz and to 100Hz. The jumpy frames are always there. Some settings they are not too bad. But I compare it to my other laptop, which is one model earlier but with 60Hz display, and it works fine with the same setup. Nice and smooth.

So at this stage, my only solution is to get a new laptop that is only 60Hz display. Unless anyone has any other ideas.

Laptop has the latest drivers based on the ASUS website.

Note: If it was just one external monitor I would upgrade that, but I work in a lot of different places where the external is supplied with the event. So changing the external is not an option.

When i google, there are many people complaining about mixed Refresh rates on Windows 10. Apparently this started after they upgraded from Windows 7. I don't have any experience with that, but don't want to go backwards in OS.

Update 6th April. The next build of Windows 10 Build 19041 has a major improvement, but does not fix completely. Had to join the Windows Insider Program to get the new build which is not out for retail yet. This new version allows smooth movement on the internal 144Hz screen when an external 60Hz is connected, but the 60Hz is not smooth. Nearly, but not quite as smooth as a complete 60Hz system. It is close to workable, however, if you want to duplicate the 144Hz desktop with a 60Hz monitor, then the original fault comes back. Ie the 60Hz as well as the internal 144Hz monitor both become jumpy.