Daisy chaining two 27" 5k monitors over DisplayPort 1.4?

[scottrblock]

Hi, I have a 2021 14" m1 mbp, and would like to connect it to two 5120x2880 monitors. I know I cannot daisy chain two LG Ultrafine 5ks, or two Apple Studio Displays, but I wasn't sure if I could daisy chain two PROLITE XB2779QQS-S1s. According to this thread, they use a single DisplayPort 1.4 (HBR3) signal, whereas the LG and Apple ones use DP1.2 and HBR2.

I was hoping someone more knowledgable than me can confirm if this would work, and how I would set it up. I'm not really sure if a normal DP -> thundetbolt cords/adapters would work, or if I need some sort of dock with an external GPU? I'd love to understand my options a bit better.

My goal is to plug one cord into my laptop and have it charge, and output to both monitors at 5k.

Also more generally, if anyone has these Prolite monitors with a MBP, would love to hear how they work. If this daisy chaining doesn't work, I'm not sure if I'd want these or the LG 5k's. It seems crazy to me that the Studio Display's, after all this time and for all this money, dont have DP 1.4. Maybe they'll release something in June or whenever that will fix this.

 

[BigBlur]

Hi, I have a 2021 14" m1 mbp, and would like to connect it to two 5120x2880 monitors. I know I cannot daisy chain two LG Ultrafine 5ks, or two Apple Studio Displays, but I wasn't sure if I could daisy chain two PROLITE XB2779QQS-S1s. According to this thread, they use a single DisplayPort 1.4 (HBR3) signal, whereas the LG and Apple ones use DP1.2 and HBR2.

These likely won't work for daisy chaining either. The issue is that macOS doesn't support MST (multi-stream transport), which is needed for daisy chaining over DisplayPort. With the Intel-based Macs, it's possible to daisy chain via DP when using Windows, but not macOS. So the hardware support was/is there...just not the software/OS support. Who knows if Apple will ever add it in.

Daisy chaining with macOS is currently only possible with Thunderbolt displays that have multiple Thunderbolt ports to support it.

I was hoping someone more knowledgable than me can confirm if this would work, and how I would set it up. I'm not really sure if a normal DP -> thundetbolt cords/adapters would work, or if I need some sort of dock with an external GPU? I'd love to understand my options a bit better.

My goal is to plug one cord into my laptop and have it charge, and output to both monitors at 5k.

Even if you get a dock, you still wouldn't be able to daisy chain. M1 Macs also don't support eGPUs either. There are docks can drive two 4k displays with a single cable, but you cannot drive two 5k displays from a single dock/Thunderbolt port. To achieve your goal of plugging one cable into your Mac, I think something has to give. Either go down to dual 4k (and use a dock), or plug in two cables to do dual 5k (with or without a dock).

This thread has some good info.

Thunderbolt dock that supports two LG 5k displays?

Hi all, I've got two 27-inch LG UltraFine 5K displays and I'd like to connect them to my MacBook Pro 14" M1. Has anyone been successful in using two LG 5k displays via a Thunderbolt dock? I've got the Sonnet Echo 11 Thunderbolt 4 dock and it definitely does not work (despite Sonnet's website...

forums.macrumors.com

 

[scottrblock]

cool thanks, two cables it is!

 

[scottrblock]

er @BigBlur what about the last doc linked in that thread — https://www.sonnettech.com/product/echo11-thunderbolt4-dock/overview.html. It says it can drive two pro display XDR's. Could it drive two 5ks? Or still a macOS issue?

 

[joevt]

er @BigBlur what about the last doc linked in that thread — https://www.sonnettech.com/product/echo11-thunderbolt4-dock/overview.html. It says it can drive two pro display XDR's. Could it drive two 5ks? Or still a macOS issue?

Any Thunderbolt 4 dock or hub should allow connecting two 5K displays or 6K displays if the displays don't use more than one DisplayPort connection each and don't use more than HBR2 link rate each. They'll need to use DSC to get full color and 60Hz (4:2:0 would also work but doesn't really count as full color and full resolution). The Apple Studio and XDR displays use DSC so they should work if your GPU supports DSC (the M1 Mac GPUs support DSC).

Thunderbolt 3 docks that use Titan Ridge should also be able to do that but one display will need to be connected without Thunderbolt.

The macOS issue is regarding MST. A Thunderbolt dock doesn't have MST or if it does, then you won't be using MST to support more than one display in macOS. For example, the HP Thunderbolt Dock G2 uses Titan Ridge and has an MST hub controlling a USB-C port and two DisplayPort ports. For macOS, you can connect one display to the USB-C port and the second display to the downstream Thunderbolt port which is not part of the MST hub. In Windows, you would do the same, but maybe you could connect two displays to the MST hub - the input to the MST hub is 25.92 Gbps - 5K60 with DSC is 11.2 Gbps and 6K60 with DSC is 15.4 Gbps so that wouldn't work unless you change the 6K60 display to 5K60 or reduce the DSC target bpp from 12bpp to 11bpp but the MST hub might have other limits. The MST hub in Windows might work with two PROLITE displays even though they don't support DSC since the MST hub can take DSC input MST streams and decompress them for the output SST streams but the MST hub might have a limit to stop that from working (I know it can do three 4K60 displays in Windows but that's less bandwidth than two 5K60 displays).

 

[scottrblock]

Any Thunderbolt 4 dock or hub should allow connecting two 5K displays or 6K displays if the displays don't use more than one DisplayPort connection each and don't use more than HBR2 link rate each. They'll need to use DSC to get full color and 60Hz (4:2:0 would also work but doesn't really count as full color and full resolution). The Apple Studio and XDR displays use DSC so they should work if your GPU supports DSC (the M1 Mac GPUs support DSC).

Thunderbolt 3 docks that use Titan Ridge should also be able to do that but one display will need to be connected without Thunderbolt.

The macOS issue is regarding MST. A Thunderbolt dock doesn't have MST or if it does, then you won't be using MST to support more than one display in macOS. For example, the HP Thunderbolt Dock G2 uses Titan Ridge and has an MST hub controlling a USB-C port and two DisplayPort ports. For macOS, you can connect one display to the USB-C port and the second display to the downstream Thunderbolt port which is not part of the MST hub. In Windows, you would do the same, but maybe you could connect two displays to the MST hub - the input to the MST hub is 25.92 Gbps - 5K60 with DSC is 11.2 Gbps and 6K60 with DSC is 15.4 Gbps so that wouldn't work unless you change the 6K60 display to 5K60 or reduce the DSC target bpp from 12bpp to 11bpp but the MST hub might have other limits. The MST hub in Windows might work with two PROLITE displays even though they don't support DSC since the MST hub can take DSC input MST streams and decompress them for the output SST streams but the MST hub might have a limit to stop that from working (I know it can do three 4K60 displays in Windows but that's less bandwidth than two 5K60 displays).

Thanks @joevt. Do you know if the Iyama 27" 5k uses DSC? I can't seem to find that.

 

[scottrblock]

@joevt would this dock do what you're describing? https://www.caldigit.com/thunderbolt-station-4/

It only has one DP1.4 input, but I think I can just use a thunderbolt 4 → DP1.4 converter like https://www.amazon.com/Cable-Matters-DisplayPort-USB-C-Supporting/dp/B01J6DT070?th=1 ?

Would this generally work better with thunderbolt 4 or DP1.4?

 

[scottrblock]

this dell dock for example has 2 DP outs. i'm wondering if that would work better? It doesn't have tb4, so I'm not sure if everything could work from my mbp or not.

 

[joevt]

Thanks @joevt. Do you know if the Iyama 27" 5k uses DSC? I can't seem to find that.

The Iiyama is an older display so I don't think it supports DSC. I think it's limited to 5K60 8bpc using HBR3 link rate. Maybe it can do 10bpc using 4:2:2 chroma sub sampling since the EDID specifies support for 4:2:2 but it only specifies supporting 8bpc. The Apple Studio Display's EDID doesn't mention 4:4:4, 4:2:2, or 4:2:0. The Iiyama has an HDMI input that has an EDID that specifies support for 4:2:0 and 10/12 bit deep color but the EDID is not setup correctly for 4:2:0 and it doesn't have a 5K timing.

If a display doesn't support DSC itself, then it can be converted to DSC by connecting it to a DisplayPort 1.4 MST hub that can decompress DSC. The CalDigit SOHO is a DisplayPort 1.4 MST hub where the two lane HBR3 input has 75% the bandwidth of four lane HBR2 but it might be sufficient for 5K60 using DSC. There might be issues with getting 10bpc/HDR at max refresh rate but that's ok for the Iiyama. macOS might not enable DSC for the MST hub though because macOS...

@joevt would this dock do what you're describing? https://www.caldigit.com/thunderbolt-station-4/

Yes, it is a Thunderbolt 4 dock but unlike other Thunderbolt 4 docks, it only has two downstream Thunderbolt 4 ports. You can connect two displays to any of three downstream Thunderbolt/DisplayPort ports.

It only has one DP1.4 input, but I think I can just use a thunderbolt 4 → DP1.4 converter like https://www.amazon.com/Cable-Matters-DisplayPort-USB-C-Supporting/dp/B01J6DT070?th=1 ?

That's a DisplayPort output. The display signal is sent out that port to a display. You can connect one display to DisplayPort and one to Thunderbolt, or one to each Thunderbolt, or two to the same Thunderbolt using another hub/dock or a Thunderbolt to dual DisplayPort adapter.

Would this generally work better with thunderbolt 4 or DP1.4?

Not sure what you're comparing.

this dell dock for example has 2 DP outs. i'm wondering if that would work better? It doesn't have tb4, so I'm not sure if everything could work from my mbp or not.

That uses DisplayLink. You don't want that if you have other options. Since you have an M1 Pro or M1 Max, you can connect two displays without using DisplayLink. You have three Thunderbolt 4 ports, so just use two of them (using the cable you linked if the display is DisplayPort instead of Thunderbolt or USB-C), for one display each. You can easily connect two displays to a single port using a Thunderbolt dock or hub or adapter if the displays use only one HBR2 connection each (the Apple Studio Display should qualify here). The Iiyama uses HBR3 so you can't connect two of them to the same Thunderbolt port unless you can get MST+DSC to work and the MST doesn't itself use 4 lanes of HBR3 - all really unlikely for macOS so don't try it unless you're curious.

 

[Amethyst1]

I wasn't sure if I could daisy chain two PROLITE XB2779QQS-S1s.

This monitor, like the Planar IX2790, uses panels that were destined for iMacs but rejected due to quality issues. My Iiyama had many stuck green pixels. There’s a reason this monitor “only” cost $900 at the time of its release...
It requires DisplayPort 1.4 at HBR3 link rate for 5K60 at 8bpc and does not support DSC.
Unfortunately it didn’t occur to me to try a 5K timing (at a lower refresh rate) via HDMI.

 

[scottrblock]

The Iiyama is an older display so I don't think it supports DSC. I think it's limited to 5K60 8bpc using HBR3 link rate. Maybe it can do 10bpc using 4:2:2 chroma sub sampling since the EDID specifies support for 4:2:2 but it only specifies supporting 8bpc. The Apple Studio Display's EDID doesn't mention 4:4:4, 4:2:2, or 4:2:0. The Iiyama has an HDMI input that has an EDID that specifies support for 4:2:0 and 10/12 bit deep color but the EDID is not setup correctly for 4:2:0 and it doesn't have a 5K timing.

If a display doesn't support DSC itself, then it can be converted to DSC by connecting it to a DisplayPort 1.4 MST hub that can decompress DSC. The CalDigit SOHO is a DisplayPort 1.4 MST hub where the two lane HBR3 input has 75% the bandwidth of four lane HBR2 but it might be sufficient for 5K60 using DSC. There might be issues with getting 10bpc/HDR at max refresh rate but that's ok for the Iiyama. macOS might not enable DSC for the MST hub though because macOS...


Yes, it is a Thunderbolt 4 dock but unlike other Thunderbolt 4 docks, it only has two downstream Thunderbolt 4 ports. You can connect two displays to any of three downstream Thunderbolt/DisplayPort ports.


That's a DisplayPort output. The display signal is sent out that port to a display. You can connect one display to DisplayPort and one to Thunderbolt, or one to each Thunderbolt, or two to the same Thunderbolt using another hub/dock or a Thunderbolt to dual DisplayPort adapter.


Not sure what you're comparing.


That uses DisplayLink. You don't want that if you have other options. Since you have an M1 Pro or M1 Max, you can connect two displays without using DisplayLink. You have three Thunderbolt 4 ports, so just use two of them (using the cable you linked if the display is DisplayPort instead of Thunderbolt or USB-C), for one display each. You can easily connect two displays to a single port using a Thunderbolt dock or hub or adapter if the displays use only one HBR2 connection each (the Apple Studio Display should qualify here). The Iiyama uses HBR3 so you can't connect two of them to the same Thunderbolt port unless you can get MST+DSC to work and the MST doesn't itself use 4 lanes of HBR3 - all really unlikely for macOS so don't try it unless you're curious.

Thanks @joevt!

It sounds like my best option is the studio displays after all.

You can easily connect two displays to a single port using a Thunderbolt dock or hub or adapter if the displays use only one HBR2 connection each (the Apple Studio Display should qualify here).

Can you recommend a Thunderbolt dock for this? I would want to plug two Apple Studio Displays into it, and have one cord out of it plug into my m1 max MBP.

 

[joevt]

Can you recommend a Thunderbolt dock for this? I would want to plug two Apple Studio Displays into it, and have one cord out of it plug into my m1 max MBP.

Any Thunderbolt 4 dock or hub. I have the CalDigit Element Hub. It's small like other Thunderbolt 4 hubs but also includes four type A ports.

 

[scottrblock]

Any Thunderbolt 4 dock or hub. I have the CalDigit Element Hub. It's small like other Thunderbolt 4 hubs but also includes four type A ports.

Cool, thanks for all of the help @joevt!

 

[Ray&Paula]

Cool, thanks for all of the help @joevt!

Please.... Let us know how you make out with two Apple Studio Displays. I have a 16" MacBook Pro M1 Max but, I havn't bought any display yet. I wanted to daisy chain from one Apple Studio Display to an older ASUS that's not 4K by using USB-C to DisplayPort 1.2 Bottom line, I'm S.O.L.

 

[joevt]

I wanted to daisy chain from one Apple Studio Display to an older ASUS that's not 4K by using USB-C to DisplayPort 1.2 Bottom line, I'm S.O.L.

Unless you use DisplayLink but you don't want to use DisplayLink.

 

[Ray&Paula]

Thanks, appreciate the help. 👍😊

 

[Ray&Paula]

Interesting.... Check out Time Mark 10:35 of the below YouTube video. Shows using two of the MacBook Pros Thunderbolt ports. I like Joevt hub idea much, much better.

 

[Ray&Paula]

Any Thunderbolt 4 dock or hub. I have the CalDigit Element Hub. It's small like other Thunderbolt 4 hubs but also includes four type A ports.

Here's another video by CalDigit that will support two 6K Thunderbolt monitors at Time Mark 2:43
Plus many other configurations;

CalDigit TS4 Hub Website:
https://www.caldigit.com/thunderbolt-station-4/