Passing through multiple high bandwidth dsiplayport displays over thunderbolt 3
I'm trying to do a 1 wire solution for plugging in multiple monitors (2650x1440@144hz with Gsync + 1080p or 1440p secondary) to either my windows desktop (with internal GPU) and a linux laptop, and easily switch between the two.
What I'm looking at is the caldigit TS3 plus, and the OWC thunderbolt to dual displayport adapter (since the displayport port on the caldigit is only 1.2 which can't support even my primary monitor alone).
My main question is, while that adapter seems to be able to support the bandwidth of my other two monitors (doing the math vs a 5k@60 which it advertises), If I plug that into the back of the caldigit, will the GPU get utilized correctly with Gysync when being used in windows? If not, would it work if I plugged them both into separate thunderbolt ports (suboptimal, but still doable)?
@hyperhopper, both the Caldigit and the OWC have the same capability. Either will support two DisplayPort 1.2 displays. for the Caldigit you just need to add a USB-C to DisplayPort cable or adapter.
DisplayPort 1.2 is sufficient for 2560x1440 144Hz or 4K 60Hz.
The OWC's claim of 5K 60Hz is only for 5K dual cable DisplayPort 1.2 displays such as the Dell UP2715K or the HP z27q.
Like I said in the first statement, you can connect two DisplayPort 1.2 displays to the Caldigit, or to the OWC. You can connect the OWC to the Caldigit if you want to use both (the Caldigit adds USB and such). A Thunderbolt 3 cable can only send two DisplayPort signals so you cannot connect one display to the Caldigit and two more to the OWC. If you are using Windows, then you can use a MST hub to split one of the DisplayPort signals (dual 1440p 60Hz).
There are alternatives to the Caldigit and OWC that support DisplayPort 1.4 instead of DisplayPort 1.2 but they require the host desktop or laptop to use a Titan Ridge Thunderbolt 3 controller instead of a Alpine Ridge Thunderbolt controller (see HP Thunderbolt Dock G2 or Wavlink Thunderbolt 3 to Dual DisplayPort 8K adapter). It's not actually possible to get two 4 lane HBR3 signals down the same Thunderbolt 3 cable though (unless it's from a Mac and the destination is an Apple Pro Display XDR).
Talking about MST, the HP Thunderbolt G2 has a built in DisplayPort 1.4 MST hub. There are similar Thunderbolt 3 docks made by Dell I think. The HP dock supports DisplayPort 1.4 but I don't think it supports DSC yet (may need a future firmware update if a current firmware update doesn't add that feature). DSC with MST allows for much greater bandwidth for splitting the DisplayPort signal. DSC requires a Navi or RTX GPU. I think the Dell dock supports DSC.
Here's a post describing DisplayPort signals over Thunderbolt 3 (where it says HBR, it means HBR or HBR2 or HBR3 depending on the host computer).
You have to check the specs of the desktop or laptop to make sure it has two 4 lane DisplayPort signals connected to the Thunderbolt controller. Some hosts might only have one DisplayPort connection. Since you want to use Gsync, one of the DisplayPort inputs to the Thunderbolt controller has to be from an Nvidia dGPU.
As an alternative to the Caldigit or OWC, you may need to use an eGPU. Then you can connect all the displays you like to the GPU in the eGPU and forget about all this DisplayPort over Thunderbolt nonsense.
Thanks for the help @joevt !
I got the full setup put together, and it almost works:
This is the goal of how I want it all to work, and it does for the laptop use case. However, for the desktop use case, I can only get 1 monitor to receive input, depending on which is plugged into the ts3 first. To get the other monitor to work, I have to plug it into the graphics card itself (either displayport or thunderbolt works fine)
My real question is, how to fix this so that both monitors will work for the desktop as they do for the laptop. My guess is that either
A: the signal coming out of the graphics card into the motherboard is only 1 video stream to be tunneled over thunderbolt to the dock. In this case, should I be able to fix this by getting a displayport MST hub, putting two outputs from the graphics card into that hub, then the hub's output into the motherboards displayport in port? That way it would be displayport 1.4 mst being sent through thunderbolt.
B: Somehow, even though 2 monitors work with the laptop due to the laptop sending 2 streams I guess, the desktop is only sending one (potentially MST) stream, and the caldigit is not capable of splitting it. The solution in this case would be to use a OWC thunderbolt to dual displayport adapter to split it manually after the caldigit.
Does anybody have any insight into what could be happening, or what could solve it? I have done a lot of googling, specifically as to how my motherboard (GIGABYTE Z390 DESIGNARE Gigabyte (Intel LGA1151/Z390/ATX/2xM.2/Thunderbolt 3/Onboard AC Wifi/12+1 Phases Digital Vrm/Motherboard) handles displayport passthrough, but there is very little information about it.
The CalDigit does not have an MST hub so if you supply it only one DisplayPort signal, then only one display connected to the CalDigit will work.
The laptop has a Thunderbolt 3 controller with two DisplayPort inputs from the laptop's GPU so it can support two displays from the CalDigit.
The Designare has a Thunderbolt 3 controller on the motherboard that has only one DisplayPort input.
The simplest solution is to connect an MST hub to the CalDigit. But the CalDigit is Alpine Ridge based, and therefore only supports DisplayPort 1.2 output. DisplayPort 1.2 can support two 1440p displays at 60Hz but not higher than that.
Replacing the CalDigit with a Thunderbolt 3 dock that uses Titan Ridge would allow DisplayPort 1.4 output that could allow higher resolution or refresh rates but that would only work if the laptop and Designare both use Titan Ridge. The review at TweakTown says the Designare has Titan Ridge but you didn't say way laptop model you have (it needs to have Titan Ridge and a dGPU or an iGPU with Gen11 graphics).
Does the Designare have an iGPU? If it's enabled, then one output might be connected to the Thunderbolt controller and support one display while the output from the GPU powers the other display.
For best results, you may need to decide to not use Thunderbolt at least from the Designare side. Find a two display KVM (two inputs from two computers and two outputs). You can continue to use the CalDigit from the laptop side. Connect the outputs of the CalDigit to one set of inputs of the KVM. Connect the outputs of the Designare's GPU to the other set of inputs of the KVM.
However, would using something like that OWC thunderbolt to displayport adapter bypass the caldigits problem of being only DP1.2 compatible, since that adapter would be the one doing the conversion from thunderbolt to displayport? Could that potentially still work with the output from the designare, since the 2070 -> designare bandwidth should be good enough (since that should be able to handle displayport 1.4MST, which could be multiple displays)?
Yes, it's possible for Thunderbolt to transmit DisplayPort 1.4 across Alpine Ridge Thunderbolt devices as long as the final device that converts Thunderbolt to DisplayPort is Titan Ridge. However, the Thunderbolt controllers for the DisplayPort input and DisplayPort output both have to be Titan Ridge.
The OWC uses Alpine Ridge so it won't output DisplayPort 1.4. There exist Thunderbolt 3 to dual DisplayPort 1.4 adapters but it does not function as a MST hub. That would be cool for the adapter to support dual DisplayPort when there is two DisplayPort signals from Thunderbolt, and then act as an MST hub when there is only one DisplayPort signal from Thunderbolt.
The laptop has UHD Graphics 620 which is limited to DisplayPort 1.2.
Maybe you could use a Titan Ridge Thunderbolt 3 device + DisplayPort 1.4 MST hub. Connect two displays to the MST hub. Connect one of the displays to the Thunderbolt output. Then you would have the display with two inputs automatically switch to the best one. This would only work if the display disables the connection to the input that is not currently chosen.