External 4k Monitor Windows very Slow

Hi, I have a problem with my external monitor.
My configuration is:
macOS High Sierra 10.13.4
Parallels Desktop 13.3.0 (43321)
MacBook Pro 13 inch 2017 (3.1GHz i5).
Using Windows 10 with the MacBook monitor everything works perfectly. Instead, using my Samsung LU28E85KRS external monitor connected via USB C to DP, the system becomes very slow.
Parallels is currently set up as follows:
Configuration Game
CPU 2 Core
4GB Ram
1GB video memory.
Does anyone know how to solve it?

 

Hi @DavideS2 , please let us know how much free space you have on your Mac.

 

Hi Arun, thank you. I have about 120GB free of 500GB. If I run windows with a FullHD external monitor everything going good.
Buh with the 4K external monitor Windows run very slowly :-(

 

I retried to connect a full hd monitor and everything works fine now. So the system becomes very slow only when I use an external 4K monitor.
How can I do? Please, help me, thank you!

 

I'm experiencing the same problem - Macbook pro 2016 w Touch bar. External HD monitor works fine - 4K not...
Parallells - don't drop the ball on this issue please.

 

Hi @DavideS2 , please check if you experiencing the slow performance issue only with Parallels Desktop for Mac or any other application while using external monitor.

 

Hi Arun, if I use windows in bootcamp or macos with a 4k external monitor the system run very quickly. The problem is only when I use Parallels Desktop for Mac with Windows 10 VM.

 

I only experience the problem with Parallells and only when connected to an external monitor.

 

That is the setting I'm using already. I have mean time noticed that I can improve performance by changing the resolution on the external monitor to a non 4K resolution - pretty useless though.

 

Same issue here. 2019 MacBook Pro 15in 2.3 I(, 16gb, Radeon Pro 560x 4GB.
Everything runs great on an external 30in HD monitor but I switch over to my 27in 4k monitor and it is completely unusable. I mean really unusable!!! I would like to know which settings I should use on both Win10 and Parallels to improve performance.

 

Found same problems, Macbook pro 2017, 13", 16GB ram (8GB for Parallels), 1TB SSD
Everything work fine, both mac and window (parallels) when i use my mbp display, but everything gone wrong lagging, slowing every app down both of mac app and window app, when i plug my 27" 4K display monitor. Please help.