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Comment by tschellenbach | Hacker News Reader

With all the hubs I still can't get my 2017 Macbook Pro 15inch to reliably run an external monitor. (it lags every now and then). So far I didn't find out yet which of the components is actually causing it. Crazy how complex it is.

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I don't see how lag could be caused by a cable or hub. It's not like a remote desktop or VNC connection, where what flows over the cable is commands to change a stored image; there is no stored image -- every pixel is re-sent for every frame. Any lag must therefore be internal to the laptop. If you have an image on the monitor, and it isn't scrambled and the colors are right, the cable and hub are working.

You’d be surprised.

I was just last week forced to use a USB-C-to-DisplayPort cable, instead of a straightforward DP to DP cable to get a 4K monitor to work. Using the latter, the computer thought everything was fine but the screen flickered like a CRT, horizontal splits and all, and went black every 3s.

There are so many layers involved I don’t even want to think about it, and am just happy it worked...

On a marginal connection source/sink of a DP link will re-train which interrupts main link operation, causing brief lags in display. If the connection is even worse you'll get the usual black-picture-for-a-few-seconds dance.

I had all sorts of odd display problems until I discovered plugging in the adapter and then the display cable into the adapter resolved them all. Seems weird, but has been a sure fix so far.

Sounds like the adapter have some circuitry with a initiation delay involved.

Reminds me of when HDMI first started shipping and people found they had to power up their new TV and games console/BR player in a certain sequence to get HDCP to play nice...

I haven't run into any issues yet, but I may have just been lucky on my hub/cable selections. What type of video connection?

Tried display port and hdmi so far. These hubs (https://www.amazon.com/gp/product/B074TD1CRZ/ref=oh_aui_deta... https://www.amazon.com/gp/product/B06VVNN8XV/ref=oh_aui_deta...) both on this screen https://www.amazon.com/gp/product/B00YD3DBOC/ref=oh_aui_deta...

It's probably something unrelated to the hubs. Who knows though :) Many moving pieces.

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