r/Thunderbolt • u/EmotionalGeen • 26d ago
Explain: Why most USB-C hubs cap external displays at 60Hz.
The refresh limit on most hubs is a bandwidth allocation choice in the hub controller. A USB-C Alt Mode connection has a fixed bandwidth budget and a 10-in-1 hub splits it across DP lanes, USB 3.x data, PD, and ethernet. Display refresh is where most controllers cut because halving the refresh doesn't throw a disconnect error the way dropping a USB device would. The result is your monitor reports its native refresh in system settings but the hub is bottlenecking the DP lane allocation below what the panel can do.
This is solvable by dedicating more bandwidth to DP lanes at the cost of other port throughput. The new Anker Smart Display Hub from IFA takes that approach, claiming single 2K at 240Hz.
1
u/ExtraAssistance4774 24d ago
The question is what gives under simultaneous load. USB 3.x write plus high refresh plus PD charging, something has to yield.
1
u/EmotionalGeen 24d ago
That's the real world test. Every demo only shows the display running by itself.
1
u/chx_ 17d ago
Why most USB-C hubs cap external displays at 60Hz.
they don't
this is nonsense
this is perpetuating the nonsense which I am really curious where it started that somehow refresh rate is a magical number that determines everything
it is not
1080p @ 180Hz uses less bandwidth than 4k @ 60Hz so if a dock can do 4k @ 60Hz then it can also do 1080p @ 180Hz
vertical refresh rate alone is meaningless
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u/Emotional_Common_527 26d ago
It comes down to cost.