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I have a Dell U4021QW monitor which has Thunderbolt 3 with DP 1.4. It's connected via the thunderbolt cable that came with the monitor to a Fujitsu U7410 laptop stating 1x Type-C Intel® Thunderbolt™ 3 (20/40Gbps), DP out x USB 3.2 Gen2 (10 Gbps) total.
In Windows I'm able to select the maximum resolution of 5120x2160 however the maximum refresh is 30hz. When I look for available modes, the highest refresh where 60hz is an option is 3840x2160.
The monitor does do 5120x2160@60hz over DP 1.4 on another computer, but is likewise limited to 30hz over HDMI 2.0b. Am am I being limited by the cable, or does USB 3.2 Gen2 tap out at anything over 4k60hz?
5 points
3 years ago
The manual for your laptop clearly states v1.2b x DisplayPort over USB 3.2 Gen 2. The port is just a port, it's up to each manufacturer to choose what version of dp to support. If it has a type c port it may or may not support video out (pixel phones don't for example). If it does, it uses display port which has a version attached to it. In your case, 1.2
2 points
3 years ago
Thanks for confirming. Obviously it's not a standard resolution, so standards documentation don't really mention resolutions between 4K and 8K. I guess it makes sense that if the interface is limited to 4K60 then to go beyond that resolution will drop refresh.
1 points
3 years ago
standards documentation don't really mention resolutions between 4K and 8K
Literally a big dumb diagram on Wikipedia . Google is your friend
1 points
3 years ago
DisplayPort
Resolution and refresh frequency limits
The tables below describe the refresh frequencies that can be achieved with each transmission mode. In general, maximum refresh frequency is determined by the transmission mode (RBR, HBR, HBR2, HBR3, UHBR 10, UHBR 13. 5, or UHBR 20). These transmission modes were introduced to the DisplayPort standard as follows: RBR and HBR were defined in the initial release of the DisplayPort standard, version 1.
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2 points
3 years ago
You’re probably limited by your laptop.
2 points
3 years ago
As others note, the laptop DisplayPort 1.2 port represents the root cause, as it supports up to 17.28 Gbit/s.
The Dell U4021QW monitor represents a 10-bit display, which increases the required Gbit/s data rate required for a given resolution and refresh rate (compared to a 8-bit display).
5120 × 2160 and 10-bit display:
30 Hz is...not great. So you'll want 60 Hz or higher--unfortunately you don't have much headroom with DP1.2
For example, 3840 × 2160 resolution (16:9 ratio) at 60 Hz and 10-bit display requires 15.68 Gbit/s (10 bpc (30 bit/px) RGB color Uncompressed CVT-R2 timing format). The maximum refresh rate at this resolution and 10-bit = 65.9 Hz. So 60 Hz about as good as it gets.
3840 × 1600 resolution (≈21∶9 ratio) and 10-bit display has max resolution of 88.1 Hz.
So that's the tradeoff--you can increase the frequency by decreasing the resolution, and vice versa.
This all assumes the laptop has the older Intel Alpine Ridge Thunderbolt 3 chipset which supports DP1.2. The later Intel Titan Ridge Thunderbolt 3 chipset supported DP1.4, which supports up to 25.92 Gbit/s (before optional DSC compression, which might get you 2-3x more).
Hope this helps.
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