Daisy Chain Pro Display XDR

mattnfg1

macrumors newbie
Original poster
Dec 29, 2019
7
2
Hi All.

Can anyone help me with this query. Im looking into connecting both a Pro Display XDR and a Thunderbolt Display to my MBP 16" (maxed out).

Will it be possible to daisy chain the TB Display to the back of the Pro Display XDR (I have the TB2 to TB3 adaptor which I use on the TB Display at the moment).

There seems to be conflicting info on this on the web. All the previews from June (when the XDR was announced) say that daisy chain is supported, however the display only has one TB3 port (the rest being USB C) so surely this wont work and I will have to plug in the Pro Display XDR and TB Display separately into ports on the MBP?

If this is the case, does anyone know if I can plug them in the 2 USB C ports on the same side or if they will need to go in different sides?

Thanks
 

adamwathan

macrumors newbie
Feb 5, 2018
22
22
Cambridge, Ontario, Canada
Definitely can't daisy chain because like you said the three ports are USB C, not Thunderbolt 3. I realized this myself when trying to connect my CalDigit TS3 dock to the display and finding it didn't work of course.
 

Nomad110

macrumors regular
Jun 16, 2012
121
27
Hi All.

Can anyone help me with this query. Im looking into connecting both a Pro Display XDR and a Thunderbolt Display to my MBP 16" (maxed out).

Will it be possible to daisy chain the TB Display to the back of the Pro Display XDR (I have the TB2 to TB3 adaptor which I use on the TB Display at the moment).

There seems to be conflicting info on this on the web. All the previews from June (when the XDR was announced) say that daisy chain is supported, however the display only has one TB3 port (the rest being USB C) so surely this wont work and I will have to plug in the Pro Display XDR and TB Display separately into ports on the MBP?

If this is the case, does anyone know if I can plug them in the 2 USB C ports on the same side or if they will need to go in different sides?

Thanks
No this is not possible. The display has one Thunderbolt 3 input and 3 USB C inputs. You must have a home run from either side of your 16” MacBook Pro going directly into each display. Remember that your MBP has a separate controller for both thunderbolt ports on the left and right side. One controller can not drive two displays so you will need to have one cable plugged into one of the ports on the left and right side in order to drive bith displays correctly. The on board SMC will take power from one of the two displays to charge your MacBook Pro at 97 watts.
 

ruslan120

macrumors 65816
Jul 12, 2009
1,127
838
Definitely can't daisy chain because like you said the three ports are USB C, not Thunderbolt 3. I realized this myself when trying to connect my CalDigit TS3 dock to the display and finding it didn't work of course.
Did Mac -> CalDigit -> Display work?
 

adamwathan

macrumors newbie
Feb 5, 2018
22
22
Cambridge, Ontario, Canada
Did Mac -> CalDigit -> Display work?
I just tried this for the first time and to my shock it actually appears to work at full 6K! I don't know why I had written this off without even trying it.

I think the only downside to this is that the TS3 is only sending 85W to the MBP, whereas the XDR can send the full 96W.

Anyone know of a bullet proof way I could test/confirm that I'm truly getting the same resolution/performance when connecting the display through the TS3 as I am when connecting it directly?
 

kid2010

macrumors regular
Sep 12, 2013
109
53
I just tried this for the first time and to my shock it actually appears to work at full 6K! I don't know why I had written this off without even trying it.

I think the only downside to this is that the TS3 is only sending 85W to the MBP, whereas the XDR can send the full 96W.

Anyone know of a bullet proof way I could test/confirm that I'm truly getting the same resolution/performance when connecting the display through the TS3 as I am when connecting it directly?
Try connect a USB-C (USB 3.2) drive to TS3 and do a speed test and see if it still maintain the similar speed?
 

elliottcable

macrumors member
Apr 7, 2007
37
4
Chicago, IL
Did any XDR owners ever get to trying this? This might, actually, be the *only way* to move an XDR more-than-two-meters away from a Mac, at the moment … given that you can't extend cables, can't buy TB3 cables longer than 2 metres, and Corning got out of the optical-active-cabling market …
 

joevt

macrumors 65816
Jun 21, 2012
1,390
679
Anyone know of a bullet proof way I could test/confirm that I'm truly getting the same resolution/performance when connecting the display through the TS3 as I am when connecting it directly?
Output from AGDCDiagnose, or DisplayDiagnose, or SwitchResX current resolution timing info.
 

elliottcable

macrumors member
Apr 7, 2007
37
4
Chicago, IL
So, I've received an XDR earlier than expected, and was able to test this for myself.

Unfortunately, *no configuration I tried* could achieve better than 5k (as reported by option-clicking "Scaling" in the Displays preferences) when daisy-chained over 2m 40Gbps cables. I tried a few different cables, as well as a few different dual-port Thunderbolt devices in the middle: no dice.

Apparently, there's literally no way to move a Pro Display XDR more than 2 meters away from the rear of your rack. >,>
 

straightMacin

macrumors regular
Dec 6, 2019
104
64
Chicago, IL
So, I've received an XDR earlier than expected, and was able to test this for myself.

Unfortunately, *no configuration I tried* could achieve better than 5k (as reported by option-clicking "Scaling" in the Displays preferences) when daisy-chained over 2m 40Gbps cables. I tried a few different cables, as well as a few different dual-port Thunderbolt devices in the middle: no dice.

Apparently, there's literally no way to move a Pro Display XDR more than 2 meters away from the rear of your rack. >,>
What cables and what TB devices did you try?
 

macpro2000

macrumors 6502a
Apr 20, 2005
955
573
Apple-highlights-from-wwdc19-p.jpeg


WWDC a little false advertising then? Because there's no way that far XDR is within 2m of the Mac Pro.
 

straightMacin

macrumors regular
Dec 6, 2019
104
64
Chicago, IL
View attachment 897119

WWDC a little false advertising then? Because there's no way that far XDR is within 2m of the Mac Pro.
Each XDR is 28.7 inches wide. The Thunderbolt plug is offset from the center by about 5 inches. That means the far left monitor’s Thunderbolt plug is ~77 inches from the right edge of the right monitor. That leaves under 2 inches of slack for the cable to reach the Mac Pro.

Maybe they were using their mythical 3m Pro cable they advertised as an accessory?
 
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macpro2000

macrumors 6502a
Apr 20, 2005
955
573
Each XDR is 28.7 inches wide. The Thunderbolt plug is offset from the center by about 5 inches. That means the far left monitor’s Thunderbolt plug is ~77 inches from the right edge of the right monitor. That leaves under 2 inches of slack for the cable to reach the Mac Pro.

Maybe they were using their mythical 3m Pro cable they advertised as an accessory?
Yea, even if the Mac Pro was flush against the right side of the far right display, it still wouldn't reach.
 

elliottcable

macrumors member
Apr 7, 2007
37
4
Chicago, IL
How about this?

I'd love that to be a solution, but it's been reported elsewhere on these forums that that's no dice — the XDR only renders at 5k over the Areca cable, for unknown reasons.

What cables and what TB devices did you try?
Two XDR cables (that came with the XDRs), a Belkin active 40Gbps 2m cable, and a 40Gbps 0.5m passive cable that came with a Sonnet enclosure a couple of years ago; and I tried the CalDigit TS3+ mentioned above and a Universal Audio Apollo X-series TB3 audio-interface as the "intermediate" devices for daisy-chaining. No dice. )=
View attachment 897119

WWDC a little false advertising then? Because there's no way that far XDR is within 2m of the Mac Pro.
Based on the 2m cable I'm holding right now, I really think that would reach — it'd definitely not be touching the desk or routed beautifully, but I easily believe it'd *reach*, just barely.

That said, I suspect they'd route the things to a second Mac Pro underneath the table *anyway*. ¯\_(ツ)_/¯
 

AppelGeenyus

macrumors member
Nov 3, 2019
47
34
I don't think daisy chaining through CalDigit TS3+ would work because it doesn't have Titan Ridge, but even if it did the dock would be rendered mostly useless due to lack of bandwidth. The same issue would apply to any other intermediate device.

All of the "Pro" TB3 cables Apple mentioned were scrubbed from the website, not sure why they would remove the shorter lengths but I can totally understand why the 3m would be removed. In my experience even active 2m TB3 cables are flaky at best. I don't think 3m is even within the TB3 spec.
 

joevt

macrumors 65816
Jun 21, 2012
1,390
679
I don't think daisy chaining through CalDigit TS3+ would work because it doesn't have Titan Ridge, but even if it did the dock would be rendered mostly useless due to lack of bandwidth. The same issue would apply to any other intermediate device.
I am pretty sure that HBR3 DisplayPort streams can be sent across intermediate Thunderbolt 3 devices. It's only the first controller (with the DisplayPort input) and the last controller (with DisplayPort output) that need to be Titan Ridge. Sending two HBR3 DisplayPort streams might be a different story though.

The point of the dock in this situation is to extend the range of the XDR, so it doesn't matter if it's useless. You might want a more useless/less costly Thunderbolt device for this role, though.

But there's no point if an intermediate Thunderbolt 3 device stops the XDR from working.
adamwathan said it worked but didn't provide evidence of 6K.
elliottcable said it doesn't work with a couple intermediate devices including the same CalDigit TS3 Plus dock that adamwathan used.
 

AppelGeenyus

macrumors member
Nov 3, 2019
47
34
I am pretty sure that HBR3 DisplayPort streams can be sent across intermediate Thunderbolt 3 devices. It's only the first controller (with the DisplayPort input) and the last controller (with DisplayPort output) that need to be Titan Ridge. Sending two HBR3 DisplayPort streams might be a different story though.

The point of the dock in this situation is to extend the range of the XDR, so it doesn't matter if it's useless. You might want a more useless/less costly Thunderbolt device for this role, though.

But there's no point if an intermediate Thunderbolt 3 device stops the XDR from working.
adamwathan said it worked but didn't provide evidence of 6K.
elliottcable said it doesn't work with a couple intermediate devices including the same CalDigit TS3 Plus dock that adamwathan used.
Sorry I should have been more specific, yes I was referring to the requirements for XDR display specifically. I would just assume trying to pass 2x HBR3 DP 1.4 through a lesser intermediate controller will never work, even if it is technically possible. Though the capability/compatibility situation of TB3/DP/USB-C is truly ridiculous, so who knows.
 

elliottcable

macrumors member
Apr 7, 2007
37
4
Chicago, IL
Honestly, this is pretty hugely high-priority for me; so I'm happy to purchase-and-test-and-return another intermediate device — does anybody know of any third-party devices with A. a downstream port and 2. the Titan Ridge controller? /=

I will say that I have my doubts, though. I'm pretty sure that's not how the daisy-chaining works. )=
 

ruslan120

macrumors 65816
Jul 12, 2009
1,127
838
Just got this idea - how about a BlackMagic eGPU in between two, 2m long cables?
Expensive?, yes. Might work?
 

joevt

macrumors 65816
Jun 21, 2012
1,390
679
Honestly, this is pretty hugely high-priority for me; so I'm happy to purchase-and-test-and-return another intermediate device — does anybody know of any third-party devices with A. a downstream port and 2. the Titan Ridge controller? /=

I will say that I have my doubts, though. I'm pretty sure that's not how the daisy-chaining works. )=
Look for Thunderbolt 3 docks that are also compatible with USB-C (non Thunderbolt) computers, such as the HP Thunderbolt Dock G2.

Maybe using Titan Ridge might work but Alpine Ridge should have been sufficient.

Maybe we need to patch Apple Thunderbolt 3 drivers to allow dual HBR3 always. Linux Thunderbolt driver has code for setting DisplayPort link rate capabilities depending on connected devices. You can find the Apple kexts for the DisplayPort In and Out adapters by file name.
 

elliottcable

macrumors member
Apr 7, 2007
37
4
Chicago, IL
Anyone have a Blackmagic eGPU that can test with 2x 2m cables (one from Mac to eGPU, other from eGPU to XDR)?
I mean, that'll clearly work, but also defeats the purpose, right? Then the display will be rendering off the eGPU, not off the more-powerful built-in GPU you paid a ton of money for. :p
 
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