mid-2018 rMBP15" (i7) keeps disconnecting from external 4k60Hz monitor under high load

[rchomskis]

Is this a normal behavior for my brand new rMBP15" (i7) to keep disconnecting from external 4k60Hz monitor under high load while working on video editing apps? This happens everytime I leave my macbook to process video conent (convert video files for online publishing). Don't think the problem is with my monitor or cables, because as soon as the macbook cools down the monitor starts receiving video signal from the macbook again. same thing happens with all four macbook's usbc ports, so ports are also not the culprit. Any ideas? P.S. I mostly work in clamshell mode...

 

[Thysanoptera]

What cable are you using? I’d say this is the most likely cause, and no - it is not normal.

 

[rchomskis]

What cable are you using? I’d say this is the most likely cause, and no - it is not normal.

I tried usbc-mDP and usbc-hdmi (diffrent makes) - same thing happens

 

[Thysanoptera]

I don’t really trust the description of 4k@60 in case of usb-c cables, for me it doesn’t work unless a large number of people report that it does. It requires all 4 lanes of USB-c to be connected to GPU, and the cable to support all 4 lanes, and the average video cable length of 6ft (2m) is at the border of passively transmitted 20Gbps, so it needs to be rather high quality. My guess is that the heat near the connector is enough to throw your both cables out of spec. Apple doesn’t offer own 4k@60Hz cable. You’d be better off getting an actual Thunderbolt 3 dock and driving the monitor from it, it will also help with cable mess if you're working mostly at your desk.

 

[rchomskis]

I'll try and see if 4k@30 cables would work better, or setting monitor resolution at lesser frame rate...