Lagging 4k monitors - Mac Mini 2018, thunderbolt cables

[grahamvinyl]

I have 2 4k TVs for my 2018 i5 Mac Mini. There is noticeable lag with keyboard/mouse inputs.

When i used just 1 display (the same TV) with HDMI to HDMI, this was not an issue. But adding a 2nd monitor with thunderbolt caused more problems (no waking from sleep, monitors not being in correct order despite trying to swap them, lag on thunderbolt if I remember correctly).

When both monitors are fed with thunderbolt, everything is fine but the lag.

I have tried every resolution setting trying to fix this.

Not sure what else to try.

Thanks for the help!

 

[iZac]

the iGPU in the mini may not be able to push x2 displays at 4k 60hz. The lag you're experiencing may just be that it's running both at 30hz.

I have enough trouble with my 2018 mini getting it to run 4K 60 HDR on one screen. I didn't realise when I first got the TV that my HDMI cable was HDMI 1.4.

In the Display settings try "option clicking" the scaled button. It'll bring up custom resolutions and let you select low resolutions. Play around with that and see if you can get it running in 60hz again, it might confirm that the GPU just can't push two displays at 4k 60hz

Like I say, my 2018 mini is temperamental enough trying to get it to run one display at 4k 60 HDR and I also experience similar intermittent problems getting it to wake from sleep properly, I think it's HDR that knackers it for me.

 

[grahamvinyl]

Thanks for the reply! Yes, it looks like both TVs are at 30hz. I actually don't see an option to up that to 60hz. I'm going to try new USB C to HDMI cables that support 4x/60hz.

 

[steve217]

The weak link of the 2018 is definitely the iGPU.

If you want to drive multiple 4k monitors at 60Hz, then you may want to look into an eGPU.

 

[iZac]

Yeah it might get costly to get the 2018 driving so many pixels smoothly. I'm personally waiting for the M2 mini, which might cost just as much as an eGPU enclosure and compatible PCI graphics card. Although before Apple Silicon was announced I bought a Radeon RX 5700 for my PC tower with the plan of one day handing down to my Mac mini via an eGPU.

 

[Boyd01]

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