MP 7,1 Mac Pro 2019 Display Output Specifications for Apple/AMD GPUs

[zebity]

Hi Mac Pro (2019) and Display Users,

I am now owner of a Mac Pro 2019 with Apple/AMD W6900X MPX Module for graphics and display.

I am finding that the "Apple User Friendly" specifications for the Mac Pro 2019 / MPX GPU great at hiding what the actual output ports really support, case in point:

"AMD Radeon Pro W6900X
- Four Thunderbolt 3 ports and one HDMI port on card with support for 4K60
- Two DisplayPort connections routed to system to support internal Thunderbolt 3 ports
- Support for up to six 4K displays, three 5K displays, or three Pro Display XDRs"

What I want to know are the exact technical specifications for the "Thunderbolt 3" Display ports.

I read:
- all of this 8K Display thread: https://forums.macrumors.com/thread...-2-0-displays-on-mac-pro-yes-you-can.2309750/
- this apple technical overview: https://www.apple.com/by/mac-pro/pdf/Mac_Pro_White_Paper_Aug_2021.pdf
- and this cable/adaptor guide: https://support.apple.com/en-au/102477


Based on this it is readily apparent that
- all of the Mac Pro 2019 offical AMD GPUs which have an HDMI interface only support HDMI 2.0 for maximum of 4K @ 60,
- that the "Apple way" for displays is via Thunderbolt 3 and this multiplexes multiple protocols including DisplayPort via single connector

The "Mac Pro Technical Overview" says that:

For W5700X MPX:

"The Radeon Pro W5700X can drive up to three Pro Display XDR
displays, three 5K displays, or six 4K displays. When used with Pro Display
XDR, DSC is enabled, allowing the downstream USB-C ports in the display to
provide USB 3.0 (5Gb/s) bandwidth."

For W6800X & W6900X:

"The Radeon Pro W6800X and W6900X MPX Modules deliver workstation-class
graphics ideal for demanding pro applications. Based on AMD’s RDNA2
architecture, these 7nm GPUs feature compute units with 50 percent improved
performance-per-watt, a GDDR6-based memory controller, and support for
DisplayPort Display Stream Compression (DSC)."


Question 1:

So my take on this is that the Mac Pro 2019 can provide DisplayPort 1.4 specification output with DSC, is this correct ?

Question 2:

So if such a thing existed then it would be able to drive a display with 8K @ 60 via Thunderbolt 3 ?

The problem is that no such device currently exists and the closest you can get to this is the Apple XDR display which provides 6k @ 60 .

I am aware of the Dell UltraSharp 32 8K Monitor - UP3218K but this does not take Thunderbolt nor provides a single DisplayPort 1.4 with DSC capability, instead requiring 2 x DisplayPort 4K @ 60 connections to drive it.

This is not the "Apple way".

I sort of get "Thunderbolt 3" but how does the Apple Mac Pro 2019 support USB-C with DisplayPort Alt Mode ?

Question 3:

Does the Thunderbolt 3 cable/signals carry "USB-C with DisplayPort Alt Mode & DSC" in it or are all of USB, DisplayPort etc packaged/multiplex differently ?

Question 4:

I ask as if a vendor decided to sell an 8K Monitor with USB-C / DisplayPort Alt Mode interface would this work directly via the Apple Thunderbolt 3 Port or would it need an "active adaptor" to convert the Thunderbolt 3 into USB-C / DisplayPort Alt Mode signals ?

Question 5:

If a vendor decided to sell an 8K Monitor with native DisplayPort 1.4 interface, would this work with a passive cable from Apple Thunderbolt 3 Port or would it need an "active adaptor" to strip out the unwanted signals and convert to native DisplayPort ?

Question 6:

Are all the Thunderbolt 3 ports on the Mac Pro 2019 with GPU equivalent (ie whether on GPU or on I/O Adaptor) or do the GPU ones only handle Displays/Graphics while the ones of the I/O Adaptor handle other types of devices ?


Thanks in advance to any technical expert who can help here, having read the very long 8K Display thread, it would be nice to have an "Apple way" solution without need for all the cables/adaptors and complicated configuration currently required.

Cheers from Oz,


Zebity

 

[zebity]

Hi Mac Pro (2019) Users,

with further reading, including:
- Apple Pro Display XDR Overview - https://www.apple.com/pro-display-xdr/pdf/Pro_Display_White_Paper_Feb_2020.pdf
- TI article on USB Alt Mode - https://www.ti.com/lit/wp/slly021/slly021.pdf
- wikipedia articles on Thunderbolt & DisplayPort
- macOS DisplayPort bugs - https://news.ycombinator.com/item?id=28013068

Here is my go at answering (my own) questions...

Question 1: So my take on this is that the Mac Pro 2019 can provide DisplayPort 1.4 specification output with DSC, is this correct ?

----
The Mac Pro (2019) Thunderbolt 3 ports can provide support for 6K Pro in two modes:
- via uncompressed HBR3, which will consume USB bandwidth (so only get USB 2.0). This is based DisplayPort 1.3 (HBR3) specification and supported by 580X MPX, W5500X MPX (given failure to mention Titan Ridge in Apple doco for these devices I presume this is via Alpine Ridge controller)
- via compressed display stream (DisplayPort 1.4 with Display Stream Compression) while also allowing USB 3.1 bandwidth. This is as per DisplayPort 1.4 specification and requires Titan Ridge controller, which is provided by W5700X MPX, W6800X MPX, W6900X MPX, W6800X Duo MPX.
- Exactly what mode is used is based on the initial negotiation when you plug in monitor/display and this has changed with macOS releases.

So Mac Pro 2019 can output DisplayPort 1.4 with DSC via Thunderbolt 3 or via USB/DisplayPort Alternate Mode, depending on display interface, but you need to have W5700X/W6800X/W6900X MPX GPU.

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Question 2: So if such a thing existed then it would be able to drive a display with 8K @ 60 via Thunderbolt 3 ?

----
This is speculative, as it is dependent on the level of compression that can be achieved through DSC. Apparently to achieve 6K@60 does not require a high level of compression.
To get 8K@60 would require a higher level of compression than is currently required by Display Pro XDR and likely also not use significant amount of USB bandwidth to keep within 40 Gbit/s aggregate bandwidth.
So if / when someone releases a 8K DisplayPort (not HDMI) monitor/display, then assuming Apple provides macOS support then there is high probability that the latter W6X00X MPX GPUs should be able to drive it.

----

Question 3: Does the Thunderbolt 3 cable/signals carry "USB-C with DisplayPort Alt Mode & DSC" in it or are all of USB, DisplayPort etc packaged/multiplex differently ?

Question 4: I ask as if a vendor decided to sell an 8K Monitor with USB-C / DisplayPort Alt Mode interface would this work directly via the Apple Thunderbolt 3 Port or would it need an "active adaptor" to convert the Thunderbolt 3 into USB-C / DisplayPort Alt Mode signals ?

----
The Thunderbolt 3 controller will negotiate with the connected device to ensure it provides only the signals that it can handle. This is fundamental to the Thunderbolt 3 / USB-C compatibility promise. The result is that it should be possible to drive a USB-C / DisplayPort Alternate Mode display using a passive cable. The USB-C negotiation between the source (computer) and sink (display) is key element in allowing them to work together.

----

Question 5: If a vendor decided to sell an 8K Monitor with native DisplayPort 1.4 interface, would this work with a passive cable from Apple Thunderbolt 3 Port or would it need an "active adaptor" to strip out the unwanted signals and convert to native DisplayPort ?

----
My take on this is that an as long at the cable was short enough, then it should be possible to have a passive USB-C / DisplayPort Alternate Mode to DisplayPort cable. The source (computer) USB-C / DisplayPort Alternate Mode interface would have to handle the requirements to support the USB-C "flip-ability".
It seems that need for active Thunderbolt 3, USB-C DisplayPort Alternate Mode cables is to allow for longer cable lengths, not for signal conversion. Signal compatibility is covered via initial connection negotiation.
NOTE #1: HDMI is exception as it has fundamental differences in its signalling protocol (TDMS for video).
NOTE #2: Passive DisplayPort to HDMI is possible with Dual Mode DisplayPort (or DisplayPort+), which outputs HDMI signals via standard size DisplayPort interface. This is not available via USB-C.

----

Question 6:

Are all the Thunderbolt 3 ports on the Mac Pro 2019 with GPU equivalent (ie whether on GPU or on I/O Adaptor) or do the GPU ones only handle Displays/Graphics while the ones of the I/O Adaptor handle other types of devices ?

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Not sure, but given that Titan Ridge Thunderbolt 3 controller with DisplayPort 1.4 & DSC capability is on GPU, I suspect they might have different behaviour. Only testing would tell.


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Please comment and correct, as this simple set of questions required more working knowledge on Thunderbolt, DisplayPort, USB-C and Apple Mac Pro 2019 than I have,

Cheers from Oz,


Zebity