Daisy chaining the model 3

Hi Guys, I have the 4k 144Hz. I like it so much I want another. The question I have is; right now I use the USB-c port for charging, display, and USB hub for my mouse and keyboard (single cable). If I purchased another 4k 144hz, would I be able to chain the second monitor to the first using the USB-c port on the hub of the first monitor for display purposes?

1 Like

AFAIK:
Daisy chaining of video signal is only supported on model 1, not on 2 and 3 because of the scaler.

2 Likes

@Zodiac09 is correct, there is no DP output for daisy chaining on the ES07D03. It’s not really a huge deal breaker because even if it did have the output port, there is no single cable that can provide enough bandwidth to the first monitor for it to support 4K/144 and pass a 4K/144 signal to the second monitor - it’s technically impossible with the hardware available in 2021.

Daisy-chaining is really neat, but right now it’s only practical at 4K if you’re using two screens at 60Hz. It would be nice to have the option on the ES07D03 to use DP daisy chaining for two 4K/60 displays - this would be useful for users with multiple computers who only need 144Hz output from one device and are happy with 60Hz on their daisy-chained devices, but unfortunately the feature isn’t there.

2 Likes

Ok thank you, I know that I’ll need to order a hub for multiple monitors then.

So you’re aware - a hub won’t surpass this limit if you’re trying to put out two display signals from a single port. You’ll still be limited by the bandwidth of that single cable coming out of the computer.

1 Like

Here’s the technical explanation behind all of this.

When you send a video signal over a USB-C cable, it’s not actually using USB data. The physical wires inside the cable are being used for a video signal rather than USB.

The cable contains wires for 4 fast lanes and 1 slow lane. The slow lane is too slow for anything but USB 2 data (480Mbps max).

The video signal can take either 2 of these lanes, or all 4 of them. With 2 of these lanes being used you max out at 4K@60. With all 4 lanes you can get up to 4K@120.

There’s also a type of compression called DSC that lets you squeeze more data into a video signal. It’s what lets us do 4K@144 on a signal rated at 4K@120. But it’s not a miracle worker, and you won’t get 4K@120 over a signal rated at 4K@60.

Hubs and docking stations will not help here. They still have a single cable to transfer data from the computer, so that single cable becomes the limiting factor. The absolute best you’ll do is running both screens at 4K@60. However, most docking stations are more limited than that, and you’ll probably end up with both screens at 4K@30.

TL;DR: If you want to use the Spectrums at anything close to their full capabilities, you need to have a separate video cable from the video card/laptop/whatever to each Spectrum.

3 Likes

My understanding was that without DSC, 2 fast lanes are going to get you 4K@30 and 4 lanes allow 4K@60, whereas with DSC you can (as you say) push 4K@60 using 2 lanes and 4K@144 using all 4 lanes.

If your version of 4K@120 without DSC is correct, do you have a source?

The info about max resolutions is on slide 22 of this slide deck (PDF) from the USB Interface Forum.

4k@120 over 4 lanes is indeed without DSC. The bit about not getting 4K@120 over 2 lanes was a bit of an assumption though, because DSC’s compression level varies quite a bit based on the image being displayed. A quick couple of searches show various sources reporting an average compression of around 2:1.

1 Like