[SOLVED] Why linking multiple displays using USB-C?

[modeonoff]

Hi, some displays have a USB-C port at the back which manufacturers claim that we can link them together using a USB-C cable. For both Windows PC and Mac, what are the advantages in doing that besides having one less cable going directly from the display to the computer?

 

[Eximo]

Daisy chaining is all about reducing cabling. Many systems don't have as many display outputs as some people might desire for one. USB-C can carry a lot more than just display data as well.

 

[hotaru.hino]

Of note, this feature is using DisplayPort, so the following points only apply to that.

• You can have multiple outputs over a single port.
• You may not be able to run a cable from the PC to the furthest monitor. While DisplayPort doesn't specify a maximum cable length, it doesn't guarantee enough bandwidth to drive say a 1440p 165Hz monitor beyond 2 meters. Note the resolution is only an example. This may apply to say you can't have more than two 1080p 60Hz streams.

However, note that unless the daisy chaining system is using Thunderbolt, it will not carry data outside of display data. That is, you cannot daisy chain say the USB ports on the monitors this way. If the USB-C port is outputting a display signal, it's only outputting that, while Thunderbolt allows a display signal plus data.

 

[modeonoff]

If my video card has a max digital resolution of 7680x4320 which means I would only be able to run 2 monitors at 4K, will using such daisy chaining method allow me to drive more than two 4K displays at 60Hz?

 

[Glenwing]

If my video card has a max digital resolution of 7680x4320 which means I would only be able to run 2 monitors at 4K, will using such daisy chaining method allow me to drive more than two 4K displays at 60Hz?

7680×4320 is equivalent to four 4K displays. But yes in daisy-chaining the combined data rates required by the monitors but be within the capabilities of a single port.

 

[modeonoff]

7680×4320 is equivalent to four 4K displays. But yes in daisy-chaining the combined data rates required by the monitors but be within the capabilities of a single port.

I don't know why EVGA gave me that information about 7680×4320 is equivalent to two 4K displays. How did you calculate?

 

[hotaru.hino]

I don't know why EVGA gave me that information about 7680×4320 is equivalent to two 4K displays. How did you calculate?

Take a calculator and punch in 7680 * 4320 / (3840 * 2160). Or if you want, a handy Google link: https://www.google.com/search?client=firefox-b-1-d&q=7680+*+4320+/+(3840+*+2160)

 

[modeonoff]

Thank you. I will ask EVGA how they calculated to result in 2 rather than 4 displays.

 

[hotaru.hino]

Thank you. I will ask EVGA how they calculated to result in 2 rather than 4 displays.

Could just be a limitation on the video card itself. Yes, the video card could theoretically push four 4K monitors, but it may only have enough display controllers for two

 

[Glenwing]

Two 4K monitors would be the limit on a single connection, assuming 60 Hz and standard color.

 

[modeonoff]

I got a reply from EVGA. They wrote: "Your calculation is incorrect. 7680 x4320 is basically 8k resolution which is equal to 2x 4k monitors."

I am a bit confused about the two calculation methods.

 

[hotaru.hino]

I got a reply from EVGA. They wrote: "Your calculation is incorrect. 7680 x4320 is basically 8k resolution which is equal to 2x 4k monitors."

I am a bit confused about the two calculation methods.

I am too.

Ask them how they came to that. I want to see their math

 

[Glenwing]

Ok, here is a 3840×2160 display:

It has dimensions of 3840 wide by 2160 tall. That is a 4K display.

If we had two 4K displays, it would look like this:

Now, the width is twice as much, 3840 × 2 = 7680. But as you can see, the height is still the same, 2160, so the combined size is 7680×2160. So two 4K displays definitely does not give you 7680×4320.

If we stacked two more on top, we would have four 4K displays, like this:

Now, you can see both the width and the height have doubled, and we have 7680×4320, which is 8K. And as you can see, it is composed of four 4K displays.

 

[modeonoff]

Very nice explanations! I am waiting for an answer from EVGA.

I tried 3x 4K 60Hz displays (one to USB-C, one to HDMI and one to Display port to the back of my EVGA RTX2080Ti FTW3 Ultra) and it worked under normal basic productivity. However, when I tried to use Nvidia Control Panel to enable Surround option, the monitors automatically changed from 4K to much lower resolutions. What could be the problem? Can this be fixed?

Regardless of whether my GPU can fully functional when connected to 2 or 4 4K 60HZ, if I end up using 1-3 gaming monitor that is 120Hz (HDMI) and 144Hz (DP), does they work well under 60Hz? Will the number of 4K displays that are fully functional at 4K be changed? As you know, if we lower the display to resolutions other than the native resolutions, letters may not look sharp. What about running 4K displays at non-native frequency?

 

[modeonoff]

I asked them again and again. They insist on 2x4K@60Hz without an explanation on the math. I also asked about maximum frequency that each monitor will display. They tried to avoid answering that and when I complained, another agent took my case and just wrote:

"We we reiterate that the total resolution of 7680x4320 and refresh rate can be up to 240Hz - we cannot guarantee stability with what you are suggesting and can disable or even downgrade the monitor to a lower resolution yet higher refresh rate. What you are describing is a driver related issue and might be best served by contacting NVIDIA as they are the manufacturer of the driver itself. I have included their contact below "

 

[modeonoff]

Asked EVGA again. They just said my GPU only supports two 4K displays with no explanation on the math nor any reason. Sounds like they don't know what they are talking about.