One of the reasons for getting the Framework Laptop, was that I would finally have a laptop capable of supporting DisplayPort 1.4, which is a necessity for my complex 4K triple monitor setup.
This also allowed me to get rid of the previously used RTX 3060 eGPU, which would cause a lot of headaches with Linux, due to issues such as nonfunctional hotplug and so on and so on. At the end I wasn’t using it at all.
So let’s get to the setup first. I’m using 3x 4K Monitors, one of them is 120 Hz. These monitors are all connected to a Dual Monitor DisplayPort 1.4 KVM from Level1Techs. The 120 Hz Monitor has his own DisplayPort Cable, whilst the other two Monitors are connected via a DisplayPort 1.4 MST Hub to the KVM. From the KVM there are two DisplayPort cables running to each computer.
For the Framework Laptop my initial plan was as follows:
Get a Thunderbolt 4 Hub with 3x TB4 Downstream Ports
Get two USB-C to DisplayPort 1.4 Adapters
When trying to connect a single monitor first, the monitor wouldn’t light up at all but the USB Connection was functional. It seems this issue was related to the USB Port #4 on the Framework having some signaling issues or whatever. Switching to USB Port #1 resolved this issue and the monitor would light up and operate at 120 Hz no problem. When connecting the second USB-C to DisplayPort Cable the 4K 120 Hz monitor would drop down to 30 Hz and the other newly connected monitors via the MST Hub would run at 4K60 each.
So it seems like the Thunderbolt 4 Hubs do not include a MST Hub, but just act as “stupid” DisplayPort Lane Splitters. The 4K 120 Hz Monitor seems to be getting a single HBR3 (DP 1.4) Lane, whilst the MST Hub gets 4x HBR3 (DP 1.4) Lanes, due to which it can operate two 4K 60 Hz Monitors no problem.
To solve this issue I have ordered a USB-C to DisplayPort MST which should hopefully fix this issue.
I’ll report back when I got the triple 4K Monitor setup working on the framework.
That is the minimum specification for Thunderbolt 4 peripherals. At the end all Thunderbolt does is carry PCIe, DisplayPort and USB Signaling over a single cable with a total bandwidth of 40 GBit/s. In the case of Thunderbolt 4, it can carry up to 5x Lanes of DisplayPort 1.4 as outlined in my post above.
When using a so called DisplayPort Multistream Transport Hub however, you can split up a single DisplayPort 1.4 Connection (4x Lanes) into 3x individual DisplayPort 1.2+ connections each operating at 4K 60Hz. The magic sauce for this is called Display Stream Compression, which is part of the DisplayPort 1.4a standard and is supported since 10th Gen Ice Lake Graphics, so the Framework supports this aswell.
That’s a silly solution in my opinion. I don’t want cables sticking out of either side of my Laptop, that’s what Thunderbolt was invented for.
According to Thunderbolt (interface) - Wikipedia, thunderbolt 3 provides bandwidth that is only sufficient for two 4k displays at 50Hz. Once Thunderbolt 4 comes around, it looks like you might be able to use just one cable, but on the present-day Framework laptop, it looks like you’ll need more than 1 Thunderbolt cable to cover the bandwidth required.
It would be worth testing if the ports on the Framework are sufficiently independent that you can plug in the two cables at the same side of the laptop. Then at least you have cables sticking out only one side of your laptop. If you ziptie them together it will look like one (thicker) cable.
You know, there’s always the possibility that this was more due to it being Nvidia rather than it being an eGPU… unless you already tried it with an AMD GPU and the same behavior occurred.
But do your monitors support it? DSC can only work if it’s supported by both the display and the source which is key because it’s an optional part of the DP1.4 spec, not a mandatory one.
At least when DSC isn’t used. That’s the big question now - if the monitors support it or not.
Each side shares a redriver, but the ports are all provided by the controller integrated in the CPU.
I’m fully aware that it’s caused by the fact that it’s an Nvidia GPU. But back when I got the eGPU last year, there were no 6000 series cards available yet in the required form factor.
No and they don’t have to, as long as the DisplayPort Multistream Transport Hub (MST) supports DSC, which is the case.