Daisy-chaining one Thunderbolt display and one DisplayPort display

[mivasi]

Hi, I'd like to get a second display. I already have Lenovo P27u-10 with USB-C port (DisplayPort + power delivery). I know macOS doesn't support MST so I was looking for a Thunderbolt display as the second one. I found Samsung F32TU870, from the Samsung website, it seems they support chaining, however, I'm not sure if plugging the Lenovo into the Samsung and the Samsung into the Mac will work? If the Samsung display will be able to send pure DisplayPort over the USB-C cable?

I understand this is an Apple forum, I'm not really asking for help with the Samsung display specifically, but if you're running a similar setup (one TB display, one DP display), I'd love to hear what displays are you using and if you had any struggles getting it to work.

 

[Amethyst1]

If the Samsung display will be able to send pure DisplayPort over the USB-C cable?

I've had a look at its manual and it doesn't explicitly mention that this configuration will work (it mentions daisy-chaining two Thunderbolt displays), but a pure DisplayPort signal should™ be available from the second downstream Thunderbolt port because any Thunderbolt 3/4 controller can extract two DisplayPort signals from a single Thunderbolt port.

 

[xraydoc]

Hi, I'd like to get a second display. I already have Lenovo P27u-10 with USB-C port (DisplayPort + power delivery). I know macOS doesn't support MST so I was looking for a Thunderbolt display as the second one. I found Samsung F32TU870, from the Samsung website, it seems they support chaining, however, I'm not sure if plugging the Lenovo into the Samsung and the Samsung into the Mac will work? If the Samsung display will be able to send pure DisplayPort over the USB-C cable?

I understand this is an Apple forum, I'm not really asking for help with the Samsung display specifically, but if you're running a similar setup (one TB display, one DP display), I'd love to hear what displays are you using and if you had any struggles getting it to work.

This worked with the old Apple Thunderbolt display and a daisy chained mini-DisplayPort Cinema Display. Not sure if it'll work with what you have though.

 

[Amethyst1]

This worked with the old Apple Thunderbolt display and a daisy chained mini-DisplayPort Cinema Display.

You cannot daisy-chain a DisplayPort display to the Apple Thunderbolt Display because its Thunderbolt controller cannot extract the second DisplayPort signal. You need to daisy-chain another Thunderbolt Display to it... or a Thunderbolt device and connect the DisplayPort display to that.

 

[xraydoc]

You cannot daisy-chain a DisplayPort display to the Apple Thunderbolt Display because its Thunderbolt controller cannot extract the second DisplayPort signal. You need to daisy-chain another Thunderbolt Display to it... or a Thunderbolt device and connect the DisplayPort display to that.

Thanks for the correction. I forgot that one needed another TB device in the chain prior to the DP display.

 

[joevt]

Right. This is a limit of Thunderbolt 1 and Thunderbolt 2 devices - they can output one DisplayPort signal each. A second Thunderbolt device is needed (such as a dock) to output a second DisplayPort signal. The Apple Thunderbolt Display is like a Thunderbolt 1 dock with a display connected to it.

Thunderbolt 3 and Thunderbolt 4 devices can output two DisplayPort signals each. A Thunderbolt 3/4 display that has a second Thunderbolt port can provide a DisplayPort signal directly from that Thunderbolt port.

Some Thunderbolt displays, like the LG UltraFine 5K display, use two DisplayPort signals when doing 5K60 8bpc or 10bpc - each 2560x2880 half of the display uses a separate DisplayPort signal carried by the Thunderbolt connection. These displays don't have a second Thunderbolt port.

 

[mivasi]

Thank you for the technical insight, I knew absolutely nothing about how DisplayPort in Thunderbolt works. Anyway, in theory, a pure DisplayPort stream should be available on the 'TB out' port of the display because it's Thunderbolt 3 and TB3 controllers should be able to extract two streams? That sounds good, I'll let you know if it worked out or not.

 

[joevt]

Thank you for the technical insight, I knew absolutely nothing about how DisplayPort in Thunderbolt works. Anyway, in theory, a pure DisplayPort stream should be available on the 'TB out' port of the display because it's Thunderbolt 3 and TB3 controllers should be able to extract two streams? That sounds good, I'll let you know if it worked out or not.

The host Thunderbolt controller also needs to have two DisplayPort connections to the GPU. Some Thunderbolt 3 PCs only have one DisplayPort connection to the GPU.

The host GPU also needs to be able to support the number of displays you want to connect. Intel GPUs are limited to 3. Nvidia is usually 4. AMD is 4 or 6. M1 and M2 is 2 (but one is from HDMI or built-in display which leaves only one from Thunderbolt). M1 Max and Pro and Ultra allow more.

The Thunderbolt controllers of M1 and M2 Macs do have two DisplayPort connections to the GPU but won't allow two separate displays per Thunderbolt port - instead, the second DisplayPort connection is reserved for dual tile displays like the LG UltraFine 5K or Dell UP2715K. The M1 Max or Pro or Ultra have dual display support from a Thunderbolt port.