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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
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The iMac Pro is not listed as compatible with the Pro Display XDR without an eGPU. My iMac Pro has a Radeon Pro Vega 64 16 GB. That would seem to be more powerful than the Radeon Pro 580 that is in the Blackmagic eGPU. I wonder why it would not work? Can anyone shed any details on whether I will truly need an eGPU for my iMac Pro to run the Pro Display XDR?
 

Kier-XF

macrumors member
Nov 17, 2014
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It’s a pretty poor show that the flagship machine from two years ago is excluded from so many headline features, including HDR support and compatibility with the Pro Display. The iMac Pro is starting to increasingly feel like a hastily cobbled together stop gap to distract customers from Apple’s failure to produce the Mac Pro in a reasonable time frame. I had fully intended to equip mine with a pair of XDR displays, but clearly Apple know better.
 
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CWallace

macrumors G3
Aug 17, 2007
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Seattle, WA
I expect the issue is that the XDR is designed around DisplayPort 1.4 (due to the native resolution) and that did not become available on TB3 until the Titan Ridge controller which Intel released in 1H 2018. So the iMac Pro (and other non-compatible Macs) are on Alpine Ridge, which supports DisplayPort 1.2 (and therefore lacks the bandwidth to drive the XDR at native resolution).
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
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Maybe the DisplayPort version supported by the TB3 controller used in the iMac pro?

Would an eGPU solve that issue?
I expect the issue is that the XDR is designed around DisplayPort 1.4 (due to the native resolution) and that did not become available on TB3 until the Titan Ridge controller which Intel released in 1H 2018. So the iMac Pro (and other non-compatible Macs) are on Alpine Ridge, which supports DisplayPort 1.2 (and therefore lacks the bandwidth to drive the XDR at native resolution).

Thanks for the response. So then the addition of a Blackmagic eGPU would solve the problem because that eGPU has DisplayPort 1.4 built in? Because the support document does say that any Mac with that eGPU would work.
 
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CWallace

macrumors G3
Aug 17, 2007
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Seattle, WA
Kinda wild that it's a requirement though.

Yeah it's just the bandwidth requirements are so high it requires DisplayPort 1.4 to use a single TB3 cable and Titan Ridge is the first Intel TB3 controller to support DP1.4.

And note: the BlackMagic eGPUs have the TR controller. Other eGPUs may not and they probably will not work if they do not.
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
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I have an iMac Pro (2017) with Radeon Pro Vega 64 16 GB graphics. Since it cannot drive the Pro Display XDR at full 6k, I got the Blackmagic Pro eGPU (which has Radeon RX Vega 56 8 GB graphics). This is supposed to be able to handle the Pro Display XDR at full 6k. However, I am only getting 5k (5120 x 2880). I am using the TB3 cable that came with the display, and a Belkin one bought direct from Apple. Anyone have any ideas? I reset PRAM.

I tried connecting the Pro Display to the Blackmagic directly, as well as through the iMac. I really hope I can get 6k when using a Blackmagic Pro eGPU!

Edit: Ah, perhaps only the actual DisplayPort on that device is 1.4 compatible, and not its TB3 ports, so I need to connect it that way. I'll test this when I find a cable.
 
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xraydoc

macrumors demi-god
Oct 9, 2005
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I have an iMac Pro (2017) with Radeon Pro Vega 64 16 GB graphics. Since it cannot drive the Pro Display XDR at full 6k, I got the Blackmagic Pro eGPU (which has Radeon RX Vega 56 8 GB graphics). This is supposed to be able to handle the Pro Display XDR at full 6k. However, I am only getting 5k (5120 x 2880). I am using the TB3 cable that came with the display, and a Belkin one bought direct from Apple. Anyone have any ideas? I reset PRAM.

I tried connecting the Pro Display to the Blackmagic directly, as well as through the iMac. I really hope I can get 6k when using a Blackmagic Pro eGPU!

Edit: Ah, perhaps only the actual DisplayPort on that device is 1.4 compatible, and not its TB3 ports, so I need to connect it that way. I'll test this when I find a cable.
Pretty sure it’ll have to run off the eGPU’s thunderbolt 3 port.
I’d call Apple if it’s not working @ 6K.
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
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Pretty sure it’ll have to run off the eGPU’s thunderbolt 3 port.
I’d call Apple if it’s not working @ 6K.

I realized that only the actual DisplayPort connection on that Blackmagic eGPU is DisplayPort 1.4 compatible. Nothing in the technical specs for it say that any of the other ports are 1.4 compatible. So I’m buying an 8k compatible usb-c to DisplayPort cable off Amazon to try out.
 
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xraydoc

macrumors demi-god
Oct 9, 2005
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I realized that only the actual DisplayPort connection on that Blackmagic eGPU is DisplayPort 1.4 compatible. Nothing in the technical specs for it say that any of the other ports are 1.4 compatible. So I’m buying an 8k compatible usb-c to DisplayPort cable off Amazon to try out.
But the monitor needs TB3 for all the other functions to work (brightness control, the rear USB-C ports, etc.).
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
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But the monitor needs TB3 for all the other functions to work (brightness control, the rear USB-C ports, etc.).

I could make two connections in that case but I doubt it works that way. But if it doesn’t then current info about the Blackmagic working with the Pro Display on Macs without Titan Ridge may be wrong!
 
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CWallace

macrumors G3
Aug 17, 2007
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Seattle, WA
I could make two connections in that case but I doubt it works that way. But if it doesn’t then current info about the Blackmagic working with the Pro Display on Macs without Titan Ridge may be wrong!

Apple's Technical Specs for the Pro Display XDR state that the Blackmagic eGPU family is officially supported and since the XDR only has a TB3 input, that is how it should be connected. And one imagines Apple actually tested this configuration. So I would contact Apple and/or Blackmagic to find out why it is not working.
 
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joevt

macrumors 68040
Jun 21, 2012
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I realized that only the actual DisplayPort connection on that Blackmagic eGPU is DisplayPort 1.4 compatible. Nothing in the technical specs for it say that any of the other ports are 1.4 compatible. So I’m buying an 8k compatible usb-c to DisplayPort cable off Amazon to try out.
Output from the AGDCDiagnose command will tell you if the display is connected with DisplayPort 1.4 and how many lanes and what GPU ports and the EDID info.

The display uses two DisplayPort 1.4 signals over Thunderbolt 3 to support 6K. A single DisplayPort cable won't work for 6K.

Are you buying the Moshi USB-C to DisplayPort cable?
The moshi cable is bidirectional, so it should also support the DisplayPort to USB-C direction. Anyway, with a single cable, only 5K60Hz 8bpc could be supported without display stream compression. I think the XDR display only allows 4K60Hz single-link but I would have to see the EDID from the AGDCDiagnose output.

Displays using a Titan Ridge Thunderbolt 3 controller usually support both USB-C (DisplayPort only) and Thunderbolt connections. But I don't see any USB-C only Macs or iPads supported in the XDR tech specs. I found this:
It says people have used the XDR with an iPad Pro and MacBook, so it should definitely work. Just not at 6K. 5K was mentioned but they didn't check if that was just the framebuffer size or if it was running at 30Hz. It could have been a 5K framebuffer, 2560x1440 HiDPI mode, 4K60Hz timing. Another option could be chroma subsampling. SwitchResX should be used to get the timing info for the current resolution (Pixel Clock, Active, Scaled To, Scan Rate) to be sure (need to find a method to get timing pixel format).
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
76
I actually have this cable and it does not work. https://www.apple.com/ca/shop/product/HLR62ZM/A/moshi-usb-c-to-displayport-cable. With only that cable connected from the Pro Display XDR to the Blackmagic Pro eGPU, no image can be displayed.

I have ordered this cable to try. https://www.amazon.com/gp/product/B07R3ZQBS6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

So, since Apple says this is possible, I am very curious what is the intended procedure for a Mac without Titan Ridge controllers to work with the Pro Display XDR with a Blackmagic Pro eGPU?
 
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CWallace

macrumors G3
Aug 17, 2007
8,472
5,013
Seattle, WA
I would expect the tested / approved configuration is using a Thunderbolt 3 cable between the Blackmagic eGPU and the XDR display using one of the TB3 connectors on the eGPU (so one TB3 cable from your iMac Pro to the BM Pro and then another TB3 cable from the BM Pro to the XDR display).

The DisplayPort connector on the Blackmagic eGPU looks to be meant to drive 5K (or lower) displays per their product documentation, so your using the DisplayPort output of the BM eGPU to connect to the XDR via a DP to USB-C cable, that probably explains why you are only getting 5K.

So you need to be using a TB3 to TB3 cable like Apple's or Belkin's.

Another reason to use a TB3 to TB3 cable with the XDR display is that this allows DSC (Display Stream Compression) which will allow not only the 6K video signal to be carried, but also leaves enough bandwidth available to support data transfer to the XDR's USB ports.
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
76
I would expect the tested / approved configuration is using a Thunderbolt 3 cable between the Blackmagic eGPU and the XDR display using one of the TB3 connectors on the eGPU (so one TB3 cable from your iMac Pro to the BM Pro and then another TB3 cable from the BM Pro to the XDR display).

The DisplayPort connector on the Blackmagic eGPU looks to be meant to drive 5K (or lower) displays per their product documentation, so your using the DisplayPort output of the BM eGPU to connect to the XDR via a DP to USB-C cable, that probably explains why you are only getting 5K.

So you need to be using a TB3 to TB3 cable like Apple's or Belkin's.

Another reason to use a TB3 to TB3 cable with the XDR display is that this allows DSC (Display Stream Compression) which will allow not only the 6K video signal to be carried, but also leaves enough bandwidth available to support data transfer to the XDR's USB ports.

I was originally using exactly the configuration you describe, with Apple approved thunderbolt 3 cables. That did not produce 5K. I then resorted to trying to use displayport as an alternative. I’m now using that exact setup, and it’s only at 5k.

I’ll contact Apple support but something isn’t working as a plug and play solution.
 
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joevt

macrumors 68040
Jun 21, 2012
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1,381
I actually have this cable and it does not work. https://www.apple.com/ca/shop/product/HLR62ZM/A/moshi-usb-c-to-displayport-cable. With only that cable connected from the Pro Display XDR to the Blackmagic Pro eGPU, no image can be displayed.

I have ordered this cable to try. https://www.amazon.com/gp/product/B07R3ZQBS6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

So, since Apple says this is possible, I am very curious what is the intended procedure for a Mac without Titan Ridge controllers to work with the Pro Display XDR with a Blackmagic Pro eGPU?
The cable from amazon will probably behave the same as the moshi cable.

If a DisplayPort only cable doesn't work, then the XDR display probably wants USB 2.0 with the DisplayPort signal (like what the MacBook or iPad Pro would give). The Thunderbolt port of the eGPU has that capability - but then your display would be connected with Thunderbolt. There aren't a lot of options to get DisplayPort 1.4 with USB 2.0 without Thunderbolt.
- You can try a Huawei VR 2 cable but I don't know if the quality is good enough for DisplayPort 1.4 (the cable is long and thin).
- A Thunderbolt 3 dock with a USB-C port supported DisplayPort 1.4 alt mode like the HP Thunderbolt Dock G2. The port is behind a MST hub which reduces the max bandwidth by a couple MHz which is not enough to affect this use case.
- An RTX Nvidia card with a virtual link port (Boot Camp only)
- A Radeon Pro W5700 card (not available yet?)
- The Wacom Link Plus, Sunix UPD2018, and Delock 89582 are limited to DisplayPort 1.2.

Anyway, none of these non-Thunderbolt options will give 6K.


Check System Information.app:

Does the Thunderbolt section show the eGPU connected via Thunderbolt with Speed: Up to 40 Gb/s x1 and Current Link Width: 0x2 ?

Does the Thunderbolt section show the XDR connected via Thunderbolt with Speed: Up to 40 Gb/s x1 and Current Link Width: 0x2 ?

Does the Graphics/Displays section show the XDR display connected to the GPU in the eGPU?

What is the timing info for the current resolution as shown by SwitchResX? (double click the current resolution in the Current Resolutions tab of the display in SwitchResX to show Pixel Clock, Active, Scaled To, Scan Rate numbers)

Post screenshots.

The following command will show the connection information for the display:
Code:
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_a.txt 2>&1

Another reason to use a TB3 to TB3 cable with the XDR display is that this allows DSC (Display Stream Compression) which will allow not only the 6K video signal to be carried, but also leaves enough bandwidth available to support data transfer to the XDR's USB ports.
DSC is a DisplayPort feature. Not Thunderbolt. Apple mentions DSC only for the AMD Radeon Pro W5700X MPX Module for the Mac Pro 2019. The Tech specs for the XDR say that only the new MacBook Pro 16-inch allows the USB ports to work faster than USB 2.0 speed (USB 3.0 speed : 5 Gbps) which suggests that the AMD Radeon Pro 5300M and AMD Radeon Pro 5500M of the MacBook Pro also has DSC?
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
76
The cable from amazon will probably behave the same as the moshi cable.

If a DisplayPort only cable doesn't work, then the XDR display probably wants USB 2.0 with the DisplayPort signal (like what the MacBook or iPad Pro would give). The Thunderbolt port of the eGPU has that capability - but then your display would be connected with Thunderbolt. There aren't a lot of options to get DisplayPort 1.4 with USB 2.0 without Thunderbolt.
- You can try a Huawei VR 2 cable but I don't know if the quality is good enough for DisplayPort 1.4 (the cable is long and thin).
- A Thunderbolt 3 dock with a USB-C port supported DisplayPort 1.4 alt mode like the HP Thunderbolt Dock G2. The port is behind a MST hub which reduces the max bandwidth by a couple MHz which is not enough to affect this use case.

You mean this simple dock? So this would be useful because is has a USB-C DisplayPort (Data and Power Out, 15W) port? Sounds like I would connect the Pro Display to the eGPU, and then the eGPU to this dock, then output from there to the iMac Pro?

Check System Information.app:

Does the Thunderbolt section show the eGPU connected via Thunderbolt with Speed: Up to 40 Gb/s x1 and Current Link Width: 0x2 ?

Does the Thunderbolt section show the XDR connected via Thunderbolt with Speed: Up to 40 Gb/s x1 and Current Link Width: 0x2 ?

Does the Graphics/Displays section show the XDR display connected to the GPU in the eGPU?

What is the timing info for the current resolution as shown by SwitchResX? (double click the current resolution in the Current Resolutions tab of the display in SwitchResX to show Pixel Clock, Active, Scaled To, Scan Rate numbers)

Post screenshots.

Yes, the speed and link width are correct.

2019-12-21 at 8.50 PM.jpeg


It is connected to the eGPU.

2019-12-21 at 8.53 PM 2.jpeg

2019-12-21 at 8.53 PM.jpeg


The following command will show the connection information for the display:
Code:
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_a.txt 2>&1

Here is a link to a txt file with the output of AGDCDiagnose -a (too long to post).
 
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joevt

macrumors 68040
Jun 21, 2012
3,053
1,381
You mean this simple dock? So this would be useful because is has a USB-C DisplayPort (Data and Power Out, 15W) port? Sounds like I would connect the Pro Display to the eGPU, and then the eGPU to this dock, then output from there to the iMac Pro?
It's useful if you want a USB-C port that is not Thunderbolt to test non-Thunderbolt connection of Titan Ridge type Thunderbolt devices.

You said that a DisplayPort to USB-C cable (DisplayPort only signal) wouldn't work with the XDR. I said that the display might want USB 2.0 with the DisplayPort signal and suggested a means to get a USB-C port that is not Thunderbolt that will transmit a DisplayPort signal with USB 2.0.

There is no reason to do this except to satisfy curiosity (to know if it will work).


Yes, the speed and link width are correct.
It is connected to the eGPU.
All looks good.

You linked that already in the other thread.

I guess we should continue in this post since that thread is for News and Articles discussion?
 
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CWallace

macrumors G3
Aug 17, 2007
8,472
5,013
Seattle, WA
DSC is a DisplayPort feature. Not Thunderbolt. Apple mentions DSC only for the AMD Radeon Pro W5700X MPX Module for the Mac Pro 2019. The Tech specs for the XDR say that only the new MacBook Pro 16-inch allows the USB ports to work faster than USB 2.0 speed (USB 3.0 speed : 5 Gbps) which suggests that the AMD Radeon Pro 5300M and AMD Radeon Pro 5500M of the MacBook Pro also has DSC?

I guess?

John Siracusa spoke at length about DSC and the XDR display on the latest Accidental Tech Podcast and seemed to imply that the W5700X MPX module would support it with the XDR display. He did note the 580 MPX module does not support DSC because it is too old (predates it, I guess). This might also be the case for the currently-available Vega-based MPX modules.
 
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OCDMacGeek

macrumors 6502a
Original poster
Jul 19, 2007
577
76
Apple Support opened a ticket, but the "senior enterprise specialist" I was transferred to didn't know what an eGPU was, and then he went through the support doc with me and tried to claim that nowhere on there does it say an older Mac with TB3 would support 6k with the Blackmagic eGPU. I made him read it back to me until he agreed that this is exactly what the support doc says.

On the Blackmagic end, their support team only says this so far:

Thank you for contacting Blackmagic Support. I am sorry to hear that you are unable to acquire the desired 6K resolution.
In regards to the setup, most of the support is handled through apple as it is their display, are eGPU has a bit to do with it but only driven by their OS.

I will however mention that the 6K is only possible through the Thunderbolt 3 connection direct, not through any adapters, as the Display Port only supports up to 5K 60fps.
Also, you have to ensure you are on the latest OS Catalina 10.15.2 as that is the OS that supports the use of the Pro Display XDR with 6K.
Ensure that there are no other devices plugged into the eGPU only the Thunderbolt 3 cable directly to your computer, and the monitor, as bandwidth may play a factor.

Aside from that I don't currently have any additional information for you. I would suggest contacting Apple and see what they would suggest, in the mean time I am reaching out to our eGPU dev team to see if we can come up with any specific information.

If you do come up with a solution or get information from Apple, I would greatly appreciate it if you shared it with us so that we may update our notes on the setup.

Hopefully this information has been helpful. If you have any further questions feel free to ask.
 
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