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phoenixbt

macrumors member
Original poster
Sep 26, 2015
40
14
I’m looking at getting a pro display XDR and was hoping to use my caldigit TS3 dock with it and my 16” MBP. I don’t need it for the display, but rather the USB ports that I already have devices running to, sd card, and wired networking. If I’m not worried about running a display through it, can I connect the dock to one of the ports on the XDR and get the pass through ? Or if the Ts 3 won’t do it, is there another dock that would?

Thanks!
 

joevt

Contributor
Jun 21, 2012
6,782
4,110
Which 16" do you have? Which graphics? 5300M or 5500M? Which OS, Big Sur or Catalina?

The CalDigit TS3 Plus dock is an older Thunderbolt 3 dock which uses the Alpine Ridge Thunderbolt controller. The Alpine Ridge Thunderbolt controller can only be connected to a Thunderbolt port. The XDR does not have any downstream Thunderbolt ports.

Only newer Thunderbolt 3 docks with the Titan Ridge Thunderbolt controller or Thunderbolt 4 docks with the Goshen Ridge Thunderbolt controller can be connected upstream to a non-Thunderbolt USB-C port. But in that case, they will be limited to USB functionality and a single display using only two lanes of DisplayPort (instead of the usual Thunderbolt capability of two separate DisplayPort connections with 4 lanes each).

The only upstream port on the XDR is the Thunderbolt input port. That port must be connected for the display and for the downstream USB-C ports to work. You must connect the upstream Thunderbolt port of the XDR to a Thunderbolt or USB-C with DisplayPort Alt Mode port - either from a computer or from a dock.

Since you have a 5300M or 5500M, then your MacBook Pro may support DSC (except maybe 5300M doesn't support DSC, or maybe Big Sur doesn't support DSC). The XDR also supports DSC. If DSC works, then you may be able to do this setup:
MacBook Pro -> TS3 Plus -> XDR.
In that case you'll get 6K 60Hz 10bpc RGB using HBR2 (17.28 Gbps) and DSC which leaves 22 Gbps for USB from the TS3+ or XDR (which should support 5 Gbps in this case).

On the other hand, if DSC doesn't work, then you'll need to connect the XDR directly to the MacBook Pro. It will do 6K 60Hz 10bpc RGB using two HBR3 connections over Thunderbolt (39 Gbps), leaving only 1 Gbps or less for USB which might only allow 480 Mb/s USB connections (I don't remember if anyone has shown what the USB connection actually is in this case even though I've asked many times). In this case, the TS3+ needs to be connected to a different Thunderbolt port of the MacBook Pro and it will support 22 Gbps of USB from its various USB controllers. connecting USB devices to the XDR in this setup would be wasteful because they would be limited to USB 2.0 speeds (keyboard and mouse should be ok).

The reason both connection methods are limited to 22 Gbps of USB is because 22 Gbps is approximately the limit of PCIe data over Thunderbolt. The rest of the 40 Gbps is usable by DisplayPort.

Newer Thunderbolt docks with Titan Ridge or Goshen Ridge only allow 10 Gbps of USB because they only have one USB controller/port - they don't add more USB controllers because they would not be compatible with non-Thunderbolt hosts. Additional USB controllers require PCIe tunnelling. Instead, these newer docks use USB hubs for all their ports instead of USB controllers.

To discover if DSC is working, we need to examine the output of the AGDCDiagnose command.
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_XDR.txt 2>&1
To discover the info about USB, the following commands should be sufficient:
system_profiler SPUSBDataType > system_profiler_usb.txt
Code:
ioreg -filw0 | perl -0777 -pE '
		s/^(([ |]+)\+-o .*  <class .*(IOPCIDevice|AppleUSBHostController|IOUSBDevice|AppleUSBHostPort|IOUSBInterface).*), id 0x.*$/$1/mg;
		s/^(([ |]*)\+-o .*  <class .*), id 0x.*\n(\2[ |]{3} +)(?>\{\n)(.*\n)*?\3\}\n\3\n/$1\n/mg;
' \
> ioreg.txt
The ioreg command gets info about USB controllers/ports/devices/interfaces. A USB controller is a PCI device, so info about PCI devices is included.
zip the result using the Finder and post if you like.
 

phoenixbt

macrumors member
Original poster
Sep 26, 2015
40
14
Which 16" do you have? Which graphics? 5300M or 5500M? Which OS, Big Sur or Catalina?

The CalDigit TS3 Plus dock is an older Thunderbolt 3 dock which uses the Alpine Ridge Thunderbolt controller. The Alpine Ridge Thunderbolt controller can only be connected to a Thunderbolt port. The XDR does not have any downstream Thunderbolt ports.

Only newer Thunderbolt 3 docks with the Titan Ridge Thunderbolt controller or Thunderbolt 4 docks with the Goshen Ridge Thunderbolt controller can be connected upstream to a non-Thunderbolt USB-C port. But in that case, they will be limited to USB functionality and a single display using only two lanes of DisplayPort (instead of the usual Thunderbolt capability of two separate DisplayPort connections with 4 lanes each).

The only upstream port on the XDR is the Thunderbolt input port. That port must be connected for the display and for the downstream USB-C ports to work. You must connect the upstream Thunderbolt port of the XDR to a Thunderbolt or USB-C with DisplayPort Alt Mode port - either from a computer or from a dock.

Since you have a 5300M or 5500M, then your MacBook Pro may support DSC (except maybe 5300M doesn't support DSC, or maybe Big Sur doesn't support DSC). The XDR also supports DSC. If DSC works, then you may be able to do this setup:
MacBook Pro -> TS3 Plus -> XDR.
In that case you'll get 6K 60Hz 10bpc RGB using HBR2 (17.28 Gbps) and DSC which leaves 22 Gbps for USB from the TS3+ or XDR (which should support 5 Gbps in this case).

On the other hand, if DSC doesn't work, then you'll need to connect the XDR directly to the MacBook Pro. It will do 6K 60Hz 10bpc RGB using two HBR3 connections over Thunderbolt (39 Gbps), leaving only 1 Gbps or less for USB which might only allow 480 Mb/s USB connections (I don't remember if anyone has shown what the USB connection actually is in this case even though I've asked many times). In this case, the TS3+ needs to be connected to a different Thunderbolt port of the MacBook Pro and it will support 22 Gbps of USB from its various USB controllers. connecting USB devices to the XDR in this setup would be wasteful because they would be limited to USB 2.0 speeds (keyboard and mouse should be ok).

The reason both connection methods are limited to 22 Gbps of USB is because 22 Gbps is approximately the limit of PCIe data over Thunderbolt. The rest of the 40 Gbps is usable by DisplayPort.

Newer Thunderbolt docks with Titan Ridge or Goshen Ridge only allow 10 Gbps of USB because they only have one USB controller/port - they don't add more USB controllers because they would not be compatible with non-Thunderbolt hosts. Additional USB controllers require PCIe tunnelling. Instead, these newer docks use USB hubs for all their ports instead of USB controllers.

To discover if DSC is working, we need to examine the output of the AGDCDiagnose command.
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_XDR.txt 2>&1
To discover the info about USB, the following commands should be sufficient:
system_profiler SPUSBDataType > system_profiler_usb.txt
Code:
ioreg -filw0 | perl -0777 -pE '
        s/^(([ |]+)\+-o .*  <class .*(IOPCIDevice|AppleUSBHostController|IOUSBDevice|AppleUSBHostPort|IOUSBInterface).*), id 0x.*$/$1/mg;
        s/^(([ |]*)\+-o .*  <class .*), id 0x.*\n(\2[ |]{3} +)(?>\{\n)(.*\n)*?\3\}\n\3\n/$1\n/mg;
' \
> ioreg.txt
The ioreg command gets info about USB controllers/ports/devices/interfaces. A USB controller is a PCI device, so info about PCI devices is included.
zip the result using the Finder and post if you like.
Well apparently this was a loaded question haha...thank you so much for replying back in all that detail!

I have one of the first gen (2019) 16" with a 5500M, running on Big Sur. I didn't realize that on TB versions for the docks...which docks have the newer TB chips? I checked the Anker dock on Amazon, but can't tell what version it uses or which other ones are on the newer chipset.

So I guess I have two scenarios - if I just wanted to use the USB, network, and SDcard ports on the dock then I should be ok connecting something with the newer TB chips to a port on the XDR? And if I wanted to connect a second monitor in to that dock, then it would depend on if DSC is working and I might need to connect the dock directly to my MBP?

Thanks again!
 

joevt

Contributor
Jun 21, 2012
6,782
4,110
Well apparently this was a loaded question haha...thank you so much for replying back in all that detail!

I have one of the first gen (2019) 16" with a 5500M, running on Big Sur. I didn't realize that on TB versions for the docks...which docks have the newer TB chips? I checked the Anker dock on Amazon, but can't tell what version it uses or which other ones are on the newer chipset.
Thunderbolt 4 docks have 4 Thunderbolt ports (1 upstream, 3 downstream). The Thunderbolt docks with Titan Ridge claim compatibility with USB-C (non-Thunderbolt) hosts. The older Thunderbolt 3 docks with Alpine Ridge do not mention USB-C (non-Thunderbolt) hosts and require a Thunderbolt host.

A Thunderbolt dock requires an upstream Thunderbolt connection to support more than one display in macOS.

A USB-C dock (or a Thunderbolt dock connected to a USB-C host) can only support one display unless it has an MST hub, but macOS doesn't support MST for multiple displays. A USB-C dock needs to be connected to a USB-C port that supports DisplayPort Alt Mode in order to connect a display. The XDR doesn't have any downstream USB-C ports that support DisplayPort Alt Mode but at least the USB functions should work.

So, yes you could connect a Thunderbolt dock with newer TB chips (such as HP Thunderbolt Dock G2 or Thunderbolt 4 dock/hub, or any Thunderbolt 3 dock that supports being connected to a USB-C non-Thunderbolt host) to the XDR. The XDR supports up to 5 Gbps USB, and that's only if DSC is working.


So I guess I have two scenarios - if I just wanted to use the USB, network, and SDcard ports on the dock then I should be ok connecting something with the newer TB chips to a port on the XDR? And if I wanted to connect a second monitor in to that dock, then it would depend on if DSC is working and I might need to connect the dock directly to my MBP?
In the first scenario you describe, the dock cannot have any display connected to it since none of the XDR's downstream USB-C ports support DisplayPort Alt Mode.

The second scenario is for when you want to connect one or two displays to the dock and only if neither display is the XDR, or if DSC works and the XDR is connected to the Thunderbolt port of the dock and another display is connected to the DisplayPort port of the dock.
 
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