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@joevt you're right:

This is 4k, not 5k. While display preferences showed 5k resolution as an option, it looks like garbage when selected:

Looking more closely at SwitchResX, it's clearly 4k. The 5k modes are scaled:
I forgot to check the specs of your 13" MacBook Pro. It has only Intel graphics, so it only supports 4K max width from a single cable connection. It only supports DisplayPort 1.2 which has max link rate HBR2 and doesn't support DSC and doesn't support HDR (so you don't see an HDR option in 10.15.4). You don't have a USB connection so you are missing presets and brightness control features of the XDR for both of your computers.

Now here's the part that's confusing to me. Looking at AGDCDiagnose, it appears to report the framebuffer window at either 2560x1600 or 2880x1800, but what I'm seeing on the monitor looks a lot more like 4k to me. Maybe it's only showing the internal LCD framebuffer settings? What's your take?
You're looking at the EFIDisplayInfo section which is stuff that happens during boot (when the Apple symbol is drawn on the screen). 2560x1600 is the pixels for your 13" MacBook Pro's display. 2880x1800 is the pixels for a 15" MacBook Pro's display. I wonder if EFI is scaling 2880x1800 down to 2560x1600 during boot? I didn't think that was something an EFI graphics driver would do. It would make the boot graphics proportional to the 15" which might be desirable if you're anal-retentive like that.

The MacBook Pro's AGDCDiagnose output is missing the stuff that you included in the Mac Pro's AGDCDiagnose output (and vice versa).


Speaking of DisplayPort 1.2 USB-C adapters (if you don't have a GPU with USB-C output), someone pointed out this cable which may be a replacement for the Huawei VR 2 Computer Connection Cable:
It has two USB type A connections instead of one. I don't know why. I haven't tried it. It does not appear on Belkin's website. If the Huawei VR 2 Computer Connection Cable doesn't allow DisplayPort 1.4 HBR2 with DSC then this Belkin cable probably doesn't either.
 
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@joevt thanks again, appreciate the explanations. I didn't post the whole AGDCDiagnose from the Mac Pro because it exceeded the forum post length. Let me know if you need to see more on my AGDCDiagnose output, I can try to attach as a file rather than inline as code. Sounds like you've already figured out what's going on though, not sure if this would be useful.

I did a search for the part number of that Belkin cable, and while I can't read Chinese, just looking at https://item.jd.com/100010876910.html it appears that this is also a DisplayPort 1.2 cable. I suspect a better option will come out at some point.
 
I did a search for the part number of that Belkin cable, and while I can't read Chinese, just looking at https://item.jd.com/100010876910.html it appears that this is also a DisplayPort 1.2 cable. I suspect a better option will come out at some point.
All we need for proper 6K connection to XDR with USB (brightness control, presets, ...) is HBR2 with DSC (for GPUs that support DSC but don't have USB-C output). The cable just needs to pass the HBR2 signal unmolested which should be possible since DisplayPort 1.2 supports HBR2. Only one person has tried it, and they didn't post any AGDCDiagnose output to see what was happening. This Belkin cable may have the same problem or it might work.
 
All we need for proper 6K connection to XDR with USB (brightness control, presets, ...) is HBR2 with DSC (for GPUs that support DSC but don't have USB-C output). The cable just needs to pass the HBR2 signal unmolested which should be possible since DisplayPort 1.2 supports HBR2. Only one person has tried it, and they didn't post any AGDCDiagnose output to see what was happening. This Belkin cable may have the same problem or it might work.

Ah, OK, cool. Well, I ordered it, should be here in 5-10 days or so. I'll report back once it arrives.
 
Ah, OK, cool. Well, I ordered it, should be here in 5-10 days or so. I'll report back once it arrives.
You sir are a hero! Maybe you can figure out why it has two USB-A connectors (are they USB 2.0 or 3.x? does a USB device appear for either connector in System Information.app or ioreg?). Hopefully it will work. But if it doesn't, I am curious to see if the AGDCDiagnose output reports information from the cable (maybe there's a DisplayPort device inside the cable) or from the XDR (a comparison of the information).
 
The cable works! I'm running 6k no problem (HBR2+DSC) and the USB connection (via the KVM switch) allows the mac to now control the monitor color and brightness. I'm running at USB1 speeds right now, but that might be due to the KVM switch, haven't tried other cable routes yet.

One of the USB connections appears to supply power (the display won't light until it's connected) and the other is data only. The data only connector routes to the Apple display. The power-supplying connection also shows up as a Via Labs BILLBOARD device, but I can't figure out what this would be.
Code:
USB 2.0 BILLBOARD:

  Product ID:    0x0103
  Vendor ID:    0x2109  (VIA Labs, Inc.)
  Version:    7.09
  Serial Number:    0000000000000001
  Speed:    Up to 12 Mb/s
  Manufacturer:    VIA Inc.
  Location ID:    0x01430000 / 24
  Current Available (mA):    500
  Extra Operating Current (mA):    0
 
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One of the USB connections appears to supply power (the display won't light until it's connected) and the other is data only. The data only connector routes to the Apple display. The power-supplying connection also shows up as a Via Labs BILLBOARD device, but I can't figure out what this would be.
Many USB-C devices and display adapters include a USB 2.0 billboard device. If you connect such an adapter to a USB-C port that does not support DisplayPort (or whatever the alt mode that is requested, e.g. Thunderbolt), then the computer can report a message (I've seen this in Windows for example).

I have a Cable Matters USB-C to DisplayPort 1.4 adapter which calls itself "Cable Matters USB-C 8K Video Adapter" - slightly more descriptive than your "USB 2.0 BILLBOARD".

I have an Apple "USB-C Digital AV Multiport Adapter" which includes a billboard device with that name.

I have a plugable.com USB-C to VGA adapter which has a billboard device that calls itself "Hoho".

A HP Thunderbolt Dock G2 also has a billboard device called "USB Billboard Device".

Billboard devices are mentioned in the USB spec somewhere.

Maybe the Belkin uses USB power from one USB connection for the chip that combines USB and DisplayPort to USB-C then the other USB connection can be used for power/usb for the USB-C connection.
 
Hey Folks, just wanted to share that I have the Pro Display XDR working through a DisplayPort KVM switch. The KVM switch is connected to a Radeon 5700 XT in an eGPU enclosure on a 2013 Mac Pro (running at full 6k resolution), and to a 13" macbook pro (running at 5k resolution as expected). I don't think this is a big surprise to anyone as this is a DSC enabled configuration, but it's nice to see that it works. Note that KVM switching speed is slooooow, as Displayport has to re-link when you switch. Takes 20 seconds or so.

Here's the setup, in a nutshell:
  • Moshi displayport to USB-C bidirectional cable (Pro Display XDR => KVM Switch)
  • StarTech SV213DPDDUA2 DisplayPort KVM switch
  • Connection A to the Mac Pro:
    • Displayport 1.4 cable (forgot the brand, sorry)
    • Sapphire Radeon 5700 XT PCI-e GPU
    • Sonnet eGFX Breakaway Box 650 (note: the card is a VERY tight fit in this case)
    • Apple Thunderbolt 3 => 2 adapter
    • Apple Thunderbolt 2 0.5m cable (had problems with a 3rd party cable) connected to TB2 port 0
    • Mac Pro 2013 (D300 GPUs) running Catalina 10.15.4
    • Purge-wrangler v6.2.3 to enable eGPU on Thunderbolt 2
  • Connection B to the Macbook Pro:
    • Displayport 1.4 cable
    • StarTech TB3CDK2DP Thuderbolt / USB-C dock (uses the new Titan Ridge chipset, other TB3 or USB-C docks did not work)
    • MacBook Pro 13" 2019 (A1989)
Here's a snippet from AGDCDiagnose:


I have a setup very similar to yours, even the same graphics card, but the Moshi cable is only giving me 5K with the Pro Display XDR instead of 6K. Maybe you or @joevt can help me.

Here's my setup:

MBP 2019 16" -> TB3 cable -> Breakaway Box 650 -> Sapphire RX 5700 XT Nitro+ -> Moshi DP to USB-C -> Pro Display XDR

I also have the GC Titan Ridge card, and if I use it instead of the Moshi cable then I get 6K, like this:

MBP 2019 16" -> TB3 cable -> Breakaway Box 650 -> Sapphire RX 5700 XT Nitro+ -> single DP to miniDP cable -> GC Titan Ridge -> TB3 cable -> Pro Display XDR

The GC Titan Ridge setup shows me that it's possible to get 6K out of a single DP port from my 5700 XT, because that's all I have between the 5700 XT and the GC Titan Ridge: a single DP-to-miniDP cable.

But here's the problem: I don't want to use the GC Titan Ridge because I need the brightness control (the display is unusable without it, as it doesn't remember the last brightness level when I switch the cable; in the middle of the night it's like staring into a light bulb). I tried every which way to get the Titan Ridge to pass the USB connection to the MBP, to no avail.

So the next logical step is to order the Belkin cable, but I'm not very confident that it will work (at 6K) because the Moshi cable didn't work for me at 6K. The Belkin cable seems to be mostly the same as the Moshi cable, with the added USB connector(s)... but maybe I'm wrong?

Here's my partial AGDCDiagnose output (from the Moshi cable setup above) in case anyone can help me. Special note: for this I switched out the Sapphire 5700 XT for another brand of the 5700 XT (with the same results, so I know the problem is not the card). (As you mentioned the Sapphire is a VERY tight fit, so I didn't want to put it back.)

Code:
### Start: AGDC[9] 0x10000240e ###############################################
IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/PEG2@1,2/IOPP/UPSB@0/IOPP/DSB1@1/IOPP/UPS0@0/IOPP/pci-bridge@1/IOPP/pci-bridge@0/IOPP/pci-bridge@0/IOPP/display@0/AMDRadeonX6000_AmdAgdcServices/AppleGraphicsDevicePolicy/AGDPClientControl
Vendor: AMD [00001002]: DiscreteGPU [2 30000] (0)
FBs: 4, Ports: 0x1e mst:0xe ddc:0x1e aux:0xe, Streams: dp:6 dvi:4 mst:6 max:6
Framebuffers:
* 0: Address:  2.0 Stream: Enabled  Group: -1  Online   Assoc'd  MayGroup       
  1: Address:  0.0 Stream: Not Associated Group: -1                    MayGroup       
  2: Address:  0.0 Stream: Not Associated Group: -1                    MayGroup       
  3: Address:  0.0 Stream: Not Associated Group: -1                    MayGroup       
Port Capabilities:
  1: AUX, DDC, MST
* 2: AUX, DDC, MST
  3: AUX, DDC, MST
  4: DDC
Connections:
  1:
* 2: [DP 1.4 4 x HBR2]      Status: [4 x HBR2 7777]      caps [features 0x101141b, p_encoding 0xd]             Sink   OUI:000-016-250 D1baba [068-049-098-097-098-097] HW Version: 17   FW Version: 6.56
  3:
  4:
## Register Dump Port 2 - Start ##
000000: 0x14 0x14 0xc4 0x83 0x01 0x00 0x01 0xc0 0x02 0x01 0x04 0x01 0x20 0x00 0x84 0x00
  Reg: 000000: 14 : DPCD_REV: 1.4
  Reg: 000001: 14 : MAX_LINK_RATE: HBR2
  Reg: 000002: c4 : MAX_LANE_COUNT: 4, TPS3_SUPPORTED: 1, ENHANCED_FRAME_CAP: 1
  Reg: 000003: 83 : MAX_DOWNSPREAD: 0.5% down, NO_AUX_HANDSHAKE_LINK_TRAINING: 0
  Reg: 000004: 01 : NORP: 1
  Reg: 000005: 00 : DOWNSTREAMPORT_PRESENT: DWN_STRM_PORT_PRESENT: 0, DWN_STRM_PORT_TYPE: [0] DisplayPort, FORMAT_CONVERSION: 0, DETAILED_CAP_INFO_AVAILABLE: 0
  Reg: 000006: 01 : MAIN_LINK_CHANNEL_CODING: ANSI 8B/10B
  Reg: 000007: c0 : DOWN_STREAM_PORT_COUNT: DWN_STRM_PORT_COUNT: 0, MSA_TIMING_PAR_IGNORED: 1, OUI: 1
  Reg: 000008: 02 : RECEIVE_PORT0_CAP_0: LOCAL_EDID_PRESENT: 1, ASSOCIATED_TO_PRECEDING_PORT: 0
  Reg: 000009: 01 : RECEIVE_PORT0_CAP_1: BUFFER_SIZE: 64
  Reg: 00000a: 04 : RECEIVE_PORT1_CAP_0:
  Reg: 00000b: 01 : RECEIVE_PORT1_CAP_1:
  Reg: 00000c: 20 : I2C Speed: 1Mbps
  Reg: 00000d: 00 : eDP_CONFIGURATION_CAP: ALTERNATE_SCRAMBLER_RESET_CAPABLE: 0, FRAMING_CHANGE_CAPABLE: 0
  Reg: 00000e: 84 : TRAINING_AUX_RD_INTERVAL: 0 RESERVED, EXTENDED_RECEIVER_CAPABILITY_FIELD_PRESENT: YES
  Reg: 00000f: 00 : ADAPTER_CAP: FORCE_LOAD_SENSE_CAP: 0, ALTERNATE_I2C_PATTERN_CAP: 0
000020: 0x00 0x00 0x01
  Reg: 000020: 00 : FAUX_CAP: FAUX_CAP: 0
  Reg: 000021: 00 : MSTM_CAP: MST_CAP: 0
  Reg: 000022: 01 : NUMBER_OF_AUDIO_ENDPOINTS: 1
000060: 0x01 0x21 0x00 0x0f 0x0b 0x04 0x00 0x00 0x00 0x01 0x0e 0x02 0x0c 0x00 0x00 0x00
  Reg: 000060: 01 : DSC Support: 1
  Reg: 000061: 21 : DSC Algorithm revision: 33
  Reg: 000062: 00 : DSC RC Buffer Block size: 0
  Reg: 000063: 0f : DSC RC Buffer size: 15
  Reg: 000064: 0b : DSC slice Capabilities 1 : 11
  Reg: 000065: 04 : DSC Line buffer bit depth: 4
  Reg: 000066: 00 : DSC Block prediction support: 0
  Reg: 000067: 00 : DSC Maximum bit per pixel: 0
  Reg: 000068: 00 : DSC Maximum bit per pixel: 0
  Reg: 000069: 01 : DSC Decoder color format capabilities: 1
  Reg: 00006a: 0e : DSC decoder color depth capabilities: 14
  Reg: 00006b: 02 : DSC Peak Throughput: 2
  Reg: 00006c: 0c : DSC Maximum Slice width: 12
  Reg: 00006d: 00 : DSC Slice capabilities 2: 0
  Reg: 00006e: 00 : Reserved: 0
  Reg: 00006f: 00 : DSC Bits per pixel increment: 0
000090: 0x0f
  Reg: 000090: 0f : FEC Capability: 0xf
000080: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
  Reg: 000080: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000081: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000082: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000083: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000084: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000085: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000086: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000087: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000088: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 000089: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 00008a: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 00008b: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 00008c: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 00008d: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 00008e: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
  Reg: 00008f: 00 : DETAILED_CAP_INFO_AVAILABLE: DWN_STRM_PORTX_CAP: [0] DisplayPort, DWN_STRM_PORTX_HPD: 0, NON_EDID_DWN_STRM_PORTX_ATTRIBUTE: 0
000100: 0x14 0x84
  Reg: 000100: 14 : LINK_BW_SET: HBR2
  Reg: 000101: 84 : LANE_COUNT_SET: LANE_COUNT_SET 4, ENHANCED_FRAME_EN: 1
000107: 0x10
  Reg: 000107: 10 : DOWNSPREAD_CTRL: SPREAD_AMP: 1, MSA_TIMING_PAR_IGNORE_EN: 0
00010a: 0x00
  Reg: 00010a: 00 : eDP_CONFIGURATION_CAP_SET: ALTERNATE_SCRAMBLER_RESET_CAPABLE: 0, FRAMING_CHANGE_CAPABLE: 0
000111: 0x00
  Reg: 000111: 00 : MSTM_CTRL: UPSTREAM_IS_SRC:0 UP_REQ_EN:0 MST_EN:0
000120: 0x00
  Reg: 000120: 00 : FEC Configuration: 0x0
000160: 0x01
  Reg: 000160: 01 : DSC Enable: 0x1
000200: 0x41 0x04 0x77 0x77 0x01 0x05 0x22 0x22
  Reg: 000200: 41 : SINK_COUNT: SINK_COUNT 1, CP_READY: 1
  Reg: 000202: 77 : LANE0: CR_DONE: 1, CHANNEL_EQ_DONE: 1, SYMBOL_LOCKED: 1
  Reg: 000202: 77 : LANE1: CR_DONE: 1, CHANNEL_EQ_DONE: 1, SYMBOL_LOCKED: 1
  Reg: 000203: 77 : LANE2: CR_DONE: 1, CHANNEL_EQ_DONE: 1, SYMBOL_LOCKED: 1
  Reg: 000203: 77 : LANE3: CR_DONE: 1, CHANNEL_EQ_DONE: 1, SYMBOL_LOCKED: 1
  Reg: 000205: 05 : SINK_STATUS: RECEIVE_PORT_0_STATUS: 1, RECEIVE_PORT_1_STATUS: 0
  Reg: 000206: 22 : LANE0: VOLTAGE_SWING: 2, PRE-EMPHASIS: 0
  Reg: 000206: 22 : LANE1: VOLTAGE_SWING: 2, PRE-EMPHASIS: 0
  Reg: 000207: 22 : LANE2: VOLTAGE_SWING: 2, PRE-EMPHASIS: 0
  Reg: 000207: 22 : LANE3: VOLTAGE_SWING: 2, PRE-EMPHASIS: 0
00020f: 0x00
  Reg: 00020f: 00 : DSC Status: 0
000280: 0x00
  Reg: 000280: 00 : FEC Status: 0
000427: 0x00
  Reg: 000427: 00 : Secondary HPD is controlled by: [0] TCON Policy, Secondary HPD status: 0, Desired HPD state: 0, Reserved: 0
00042f: 0x01
  Reg: 00042f: 01 : DISPLAY_ROTATION: 0x1
002200: 0x14 0x14 0xc4 0x83 0x01 0x00 0x01 0xc0 0x02 0x01 0x04 0x01 0x0f 0x00 0x84 0x00
  Reg: 002200: 14 : DPCD_REV: 1.4
  Reg: 002201: 14 : MAX_LINK_RATE: HBR2
  Reg: 002202: c4 : MAX_LANE_COUNT: 4, TPS3_SUPPORTED: 1, ENHANCED_FRAME_CAP: 1
  Reg: 002203: 83 : MAX_DOWNSPREAD: 0.5% down, NO_AUX_HANDSHAKE_LINK_TRAINING: 0
  Reg: 002204: 01 : NORP: 1
  Reg: 002205: 00 : DOWNSTREAMPORT_PRESENT: DWN_STRM_PORT_PRESENT: 0, DWN_STRM_PORT_TYPE: [0] DisplayPort, FORMAT_CONVERSION: 0, DETAILED_CAP_INFO_AVAILABLE: 0
  Reg: 002206: 01 : MAIN_LINK_CHANNEL_CODING_SET: ANSI 8B/10B
  Reg: 002207: c0 : DOWN_STREAM_PORT_COUNT: DWN_STRM_PORT_COUNT: 0, MSA_TIMING_PAR_IGNORED: 1, OUI: 1
  Reg: 002208: 02 : RECEIVE_PORT0_CAP_0: LOCAL_EDID_PRESENT: 1, ASSOCIATED_TO_PRECEDING_PORT: 0
  Reg: 002209: 01 : RECEIVE_PORT0_CAP_1: BUFFER_SIZE: 64
  Reg: 00220a: 04 : RECEIVE_PORT1_CAP_0:
  Reg: 00220b: 01 : RECEIVE_PORT1_CAP_1:
  Reg: 00220c: 0f : I2C Speed: 1Kbps 5Kbps 10Kbps 100Kbps
  Reg: 00220d: 00 : eDP_CONFIGURATION_CAP_SET: ALTERNATE_SCRAMBLER_RESET_CAPABLE: 0, FRAMING_CHANGE_CAPABLE: 0
  Reg: 00220e: 84 : TRAINING_AUX_RD_INTERVAL: 0 RESERVED, EXTENDED_RECEIVER_CAPABILITY_FIELD_PRESENT: YES
  Reg: 00220f: 00 : ADAPTER_CAP: FORCE_LOAD_SENSE_CAP: 0, ALTERNATE_I2C_PATTERN_CAP: 0
068028: 0x01
  Reg: 068028: 01 : HDCP_CAPABLE: 1, REPEATER: 0
06921d: 0x02 0x00 0x02
  Reg: 06921d: 02 : VERSION: 2
  Reg: 06921f: 02 : HDCP_CAPABLE: 1, REPEATER: 0
069330: 0x00 0x00
  Reg: 069330: 00 : HDCP_Depth: 0
  Reg: 069331: 00 : HDCP_count: 0  HDCP2_0 Downstream: 0 HDCP1 Downstream: 0
069493: 0x00
  Reg: 069493: 00 : Ready: 0 , H' Available: 0, Pairing_available: 0 , Reauth_req: 0, Link Integrity: 0
## Register Dump Port 2 - End ##
## EDID Dump Port 2 - Start ##
// EDID Dump: device, 640 bytes, OK
uint8_t EDID_APP_610_ae2d[] = {
  /* 000: */  0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
  /* 008: */  0x06, 0x10, 0x2d, 0xae, 0x01, 0x14, 0x06, 0x35,
  /* 010: */  0x01, 0x1d, 0x01, 0x04, 0xc5, 0x46, 0x27, 0x78,
  /* 018: */  0x00, 0x0f, 0x91, 0xae, 0x52, 0x43, 0xb0, 0x26,
  /* 020: */  0x0f, 0x50, 0x54, 0x00, 0x00, 0x00, 0x01, 0x01,
  /* 028: */  0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
  /* 030: */  0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x42, 0xce,
  /* 038: */  0x00, 0x50, 0xf0, 0x70, 0x55, 0x80, 0x08, 0x20,
  /* 040: */  0x78, 0x00, 0xbb, 0x89, 0x21, 0x00, 0x00, 0x1a,
  /* 048: */  0x42, 0xce, 0x00, 0x50, 0xf0, 0x70, 0x16, 0x82,
  /* 050: */  0x08, 0x20, 0x88, 0x00, 0xbb, 0x89, 0x21, 0x00,
  /* 058: */  0x00, 0x1a, 0xa0, 0x5c, 0x00, 0x50, 0xa0, 0xa0,
  /* 060: */  0x39, 0x50, 0x08, 0x20, 0xb8, 0x08, 0xbb, 0x89,
  /* 068: */  0x21, 0x00, 0x00, 0x1a, 0x00, 0x00, 0x00, 0xfc,
  /* 070: */  0x00, 0x50, 0x72, 0x6f, 0x44, 0x69, 0x73, 0x70,
  /* 078: */  0x6c, 0x61, 0x79, 0x58, 0x44, 0x52, 0x04, 0xd0,
  /* 080: */  0x02, 0x03, 0x0f, 0x80, 0xe3, 0x05, 0x00, 0x00,
  /* 088: */  0xe6, 0x06, 0x01, 0x01, 0x6b, 0x6b, 0x02, 0x3c,
  /* 090: */  0xce, 0x00, 0x50, 0xf0, 0x70, 0x57, 0x80, 0x08,
  /* 098: */  0x20, 0x98, 0x00, 0xbb, 0x89, 0x21, 0x00, 0x00,
  /* 0a0: */  0x1a, 0x3d, 0xce, 0x00, 0x50, 0xf0, 0x70, 0x86,
  /* 0a8: */  0x82, 0x08, 0x20, 0x88, 0x0c, 0xbb, 0x89, 0x21,
  /* 0b0: */  0x00, 0x00, 0x1a, 0x41, 0xce, 0x00, 0x50, 0xf0,
  /* 0b8: */  0x70, 0x89, 0x82, 0x08, 0x20, 0xb8, 0x0c, 0xbb,
  /* 0c0: */  0x89, 0x21, 0x00, 0x00, 0x1a, 0x00, 0x00, 0x00,
  /* 0c8: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 0d0: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 0d8: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 0e0: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 0e8: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 0f0: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 0f8: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xbb,
  /* 100: */  0x70, 0x12, 0x79, 0x00, 0x00, 0x29, 0x00, 0x10,
  /* 108: */  0x83, 0x4d, 0xb4, 0x8b, 0xde, 0x35, 0x43, 0x41,
  /* 110: */  0x9e, 0xb6, 0x86, 0x97, 0xa0, 0x41, 0x1a, 0x9e,
  /* 118: */  0x01, 0x00, 0x0c, 0x52, 0x1b, 0x5e, 0x0f, 0x80,
  /* 120: */  0x17, 0x38, 0x0d, 0x10, 0x78, 0x4e, 0xbb, 0x7f,
  /* 128: */  0x81, 0x07, 0xfa, 0x10, 0x00, 0x04, 0x01, 0x00,
  /* 130: */  0x00, 0x7e, 0x00, 0x05, 0x3a, 0x02, 0x92, 0x81,
  /* 138: */  0x00, 0x03, 0x00, 0x28, 0xc4, 0x6c, 0x01, 0x04,
  /* 140: */  0xff, 0x13, 0x4f, 0x00, 0x07, 0x80, 0x1f, 0x00,
  /* 148: */  0x3f, 0x0b, 0x70, 0x00, 0x62, 0x00, 0x07, 0x00,
  /* 150: */  0x58, 0xf6, 0x01, 0x84, 0x7f, 0x17, 0x4f, 0x00,
  /* 158: */  0x07, 0x80, 0x1f, 0x00, 0x37, 0x0d, 0x83, 0x00,
  /* 160: */  0x75, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 168: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 170: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 178: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x25, 0x90,
  /* 180: */  0x70, 0x12, 0x79, 0x00, 0x00, 0x03, 0x00, 0x64,
  /* 188: */  0xc4, 0x6c, 0x01, 0x04, 0xff, 0x13, 0x4f, 0x00,
  /* 190: */  0x07, 0x80, 0x1f, 0x00, 0x3f, 0x0b, 0x70, 0x00,
  /* 198: */  0x62, 0x00, 0x07, 0x00, 0xa5, 0x6c, 0x01, 0x04,
  /* 1a0: */  0xff, 0x13, 0x4f, 0x00, 0x07, 0x80, 0x1f, 0x00,
  /* 1a8: */  0x3f, 0x0b, 0x72, 0x00, 0x64, 0x00, 0x07, 0x00,
  /* 1b0: */  0xb5, 0x6c, 0x01, 0x04, 0xff, 0x13, 0x4f, 0x00,
  /* 1b8: */  0x07, 0x80, 0x1f, 0x00, 0x3f, 0x0b, 0xc6, 0x02,
  /* 1c0: */  0xb8, 0x02, 0x07, 0x00, 0xbe, 0x6c, 0x01, 0x04,
  /* 1c8: */  0xff, 0x13, 0x4f, 0x00, 0x07, 0x80, 0x1f, 0x00,
  /* 1d0: */  0x3f, 0x0b, 0x5c, 0x03, 0x4e, 0x03, 0x07, 0x00,
  /* 1d8: */  0xab, 0x6c, 0x01, 0x04, 0xff, 0x13, 0x4f, 0x00,
  /* 1e0: */  0x07, 0x80, 0x1f, 0x00, 0x3f, 0x0b, 0x5f, 0x03,
  /* 1e8: */  0x51, 0x03, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 1f0: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 1f8: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x90,
  /* 200: */  0x70, 0x12, 0x79, 0x00, 0x00, 0x03, 0x00, 0x64,
  /* 208: */  0x58, 0xf6, 0x01, 0x84, 0x7f, 0x17, 0x4f, 0x00,
  /* 210: */  0x07, 0x80, 0x1f, 0x00, 0x37, 0x0d, 0x83, 0x00,
  /* 218: */  0x75, 0x00, 0x07, 0x00, 0x45, 0xf6, 0x01, 0x04,
  /* 220: */  0x7f, 0x17, 0x4f, 0x00, 0x07, 0x80, 0x1f, 0x00,
  /* 228: */  0x37, 0x0d, 0x86, 0x00, 0x78, 0x00, 0x07, 0x00,
  /* 230: */  0x52, 0xf6, 0x01, 0x04, 0x7f, 0x17, 0x4f, 0x00,
  /* 238: */  0x07, 0x80, 0x1f, 0x00, 0x37, 0x0d, 0x42, 0x03,
  /* 240: */  0x34, 0x03, 0x07, 0x00, 0x58, 0xf6, 0x01, 0x04,
  /* 248: */  0x7f, 0x17, 0x4f, 0x00, 0x07, 0x80, 0x1f, 0x00,
  /* 250: */  0x37, 0x0d, 0xf2, 0x03, 0xe4, 0x03, 0x07, 0x00,
  /* 258: */  0x4c, 0xf6, 0x01, 0x04, 0x7f, 0x17, 0x4f, 0x00,
  /* 260: */  0x07, 0x80, 0x1f, 0x00, 0x37, 0x0d, 0xf6, 0x03,
  /* 268: */  0xe8, 0x03, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 270: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  /* 278: */  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xb4, 0x90
};
## EDID Dump Port 2 - End ##
## Display Connection Stats Dump Port 2 - End ##
  Display mfgName: APP, productID: 0xae2d
  Time to EDID read: 1239
  Time to link train: 2364638
  Link training duration: 55766
  Link training status: 1
  Link training count: 2
  HDCP status: 0
  HDCP retry count: 1
  EFI w/a data: 0x0
## Display Connection Stats Dump Port 2 - End ##
### End: AGDC[9] 0x10000240e (took 0.302 sec) ################################

I think DSC is disabled with the Moshi cable (DSC Status: 0), but why??? It shows "DSC Status: 7" when I use the GC Titan Ridge (I guess that means it's enabled, which would explain why I get 6K with the GC Titan Ridge).

Also the EDID for the monitor is 0xae2d through the Moshi cable (as seen above) and 0xae22 through the GC Titan Ridge. Is there a way to override the EDID and make it report the "good" EDID when I connect the display through the Moshi cable?

Help, please!
 
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I have a setup very similar to yours, even the same graphics card, but the Moshi cable is only giving me 5K with the Pro Display XDR instead of 6K. Maybe you or @joevt can help me.

Here's my setup:

MBP 2019 16" -> TB3 cable -> Breakaway Box 650 -> Sapphire RX 5700 XT Nitro+ -> Moshi DP to USB-C -> Pro Display XDR

I also have the GC Titan Ridge card, and if I use it instead of the Moshi cable then I get 6K, like this:

MBP 2019 16" -> TB3 cable -> Breakaway Box 650 -> Sapphire RX 5700 XT Nitro+ -> single DP to miniDP cable -> GC Titan Ridge -> TB3 cable -> Pro Display XDR

The GC Titan Ridge setup shows me that it's possible to get 6K out of a single DP port from my 5700 XT, because that's all I have between the 5700 XT and the GC Titan Ridge: a single DP-to-miniDP cable.

But here's the problem: I don't want to use the GC Titan Ridge because I need the brightness control (the display is unusable without it, as it doesn't remember the last brightness level when I switch the cable; in the middle of the night it's like staring into a light bulb). I tried every which way to get the Titan Ridge to pass the USB connection to the MBP, to no avail.

So the next logical step is to order the Belkin cable, but I'm not very confident that it will work (at 6K) because the Moshi cable didn't work for me at 6K. The Belkin cable seems to be mostly the same as the Moshi cable, with the added USB connector(s)... but maybe I'm wrong?

Here's my partial AGDCDiagnose output (from the Moshi cable setup above) in case anyone can help me. Special note: for this I switched out the Sapphire 5700 XT for another brand of the 5700 XT (with the same results, so I know the problem is not the card). (As you mentioned the Sapphire is a VERY tight fit, so I didn't want to put it back.)

I think DSC is disabled with the Moshi cable (DSC Status: 0), but why??? It shows "DSC Status: 7" when I use the GC Titan Ridge (I guess that means it's enabled, which would explain why I get 6K with the GC Titan Ridge).

Also the EDID for the monitor is 0xae2d through the Moshi cable (as seen above) and 0xae22 through the GC Titan Ridge. Is there a way to override the EDID and make it report the "good" EDID when I connect the display through the Moshi cable?

Help, please!
I don't see any problems. Maybe a problem is shown in the parts you did not include. Attach the entire result (don't copy paste text).

DSC Support: 1 (means DSC is supported by the display)
DSC Enable: 0x1 (means DSC is enabled)
DSC Status: 0 (means no DSC error - or maybe you're right and it should be non-0 - I've seen 7 and 3 as working)
FEC Status: 0 (means no forward error correction error)
DISPLAY_ROTATION: 0x1 (is the display rotated? or it means the display supports rotation?)

Many DisplayPort DPCD registers are listed at
but it doesn't have DSC Status (DisplayPort 1.4 spec is not freely available; DisplayPort 1.2a spec can be found).

Reg: 000000: 14 : DPCD_REV: 1.4
Reg: 000001: 14 : MAX_LINK_RATE: HBR2
Reg: 000002: c4 : MAX_LANE_COUNT: 4, TPS3_SUPPORTED: 1, ENHANCED_FRAME_CAP: 1

DisplayPort 1.4 is supported, max link rate HBR2 is sufficient for 6K when DSC is enabled.

Reg: 000100: 14 : LINK_BW_SET: HBR2
Reg: 000101: 84 : LANE_COUNT_SET: LANE_COUNT_SET 4, ENHANCED_FRAME_EN: 1

Link rate is set to HBR2. Link width is 4 lanes. All good.

Reg: 002200: 14 : DPCD_REV: 1.4
Reg: 002201: 14 : MAX_LINK_RATE: HBR2
Reg: 002202: c4 : MAX_LANE_COUNT: 4, TPS3_SUPPORTED: 1, ENHANCED_FRAME_CAP: 1

DisplayPort 1.4 features match.

The EDID matches other ae2d that I've seen before (without HDR enabled). The ae2d variant is expected in this case (USB-C connection). It has a 6K timing. What evidence do you have that it's not working at 6K?

The ae22 variant is for Thunderbolt connection (but not for dual cable 6K).

Both EDID's have the 6K timing.

Maybe use SwitchResX to see what EDID it is seeing and the list of resolutions. Double click a resolution to show its timing info.
 
I don't see any problems. Maybe a problem is shown in the parts you did not include. Attach the entire result (don't copy paste text).

Thanks for your response. :)

Here you go (attached). Also, this was done with the MBP's lid closed so that the Pro Display XDR is the only display listed. And once again, this corresponds to my Moshi cable setup, the first one I described in my previous post (with the exception that the actual card is an 5700 XT from the XFX manufacturer instead of the Sapphire one (both cards give me the same 5K with Moshi and 6K with GC Titan Ridge).

Also, here's an additional data point. I noticed that the GC TR has a DP port built-in, so I figured, why not plug the Moshi cable there for a test? The result was that I got the same 5K as I did when plugged the Moshi cable to the DP port of the 5700 XT. In this case the Moshi cable was replacing the TB3 cable between the GC TR and the Pro Display XDR.

DISPLAY_ROTATION: 0x1 (is the display rotated? or it means the display supports rotation?)

The display was in landscape orientation at the time. I also noticed that macOS doesn't give me the option to select a rotation mode for this display in System Preferences > Displays, not even with the option+command trick (which incidentally works even for the built-in panel). Perhaps DISPLAY_ROTATION means that the display has a built-in orientation sensor - which is currently not accessible to the mac, same as the brightness controls, due to lack of USB support.

Reg: 000000: 14 : DPCD_REV: 1.4
Reg: 000001: 14 : MAX_LINK_RATE: HBR2
Reg: 000002: c4 : MAX_LANE_COUNT: 4, TPS3_SUPPORTED: 1, ENHANCED_FRAME_CAP: 1

DisplayPort 1.4 is supported, max link rate HBR2 is sufficient for 6K when DSC is enabled.

Reg: 000100: 14 : LINK_BW_SET: HBR2
Reg: 000101: 84 : LANE_COUNT_SET: LANE_COUNT_SET 4, ENHANCED_FRAME_EN: 1

Link rate is set to HBR2. Link width is 4 lanes. All good.

Reg: 002200: 14 : DPCD_REV: 1.4
Reg: 002201: 14 : MAX_LINK_RATE: HBR2
Reg: 002202: c4 : MAX_LANE_COUNT: 4, TPS3_SUPPORTED: 1, ENHANCED_FRAME_CAP: 1

DisplayPort 1.4 features match.

FYI - all of the above are identical when connected through the GC Titan Ridge (at 6K resolution).

The EDID matches other ae2d that I've seen before (without HDR enabled). The ae2d variant is expected in this case (USB-C connection). It has a 6K timing. What evidence do you have that it's not working at 6K?

The evidence is as follows.

1. With the Moshi cable, as soon as the image appears I can tell right away that everything is a little bigger on the screen. With GC Titan Ridge, everything is back to normal size (normal = same as connecting the mac directly to the Pro Display XDR with a TB3 cable).
2. Apple menu > About This Mac > Displays > Apple Pro Display XDR > shows 5120 x 2880 underneath. With GC TR, it shows 6016 x 3384.
3. System Preferences > Displays > Pro Display XDR > option+click Scaled > highest resolution is 5120 x 2880. With GC TR, it's 6016 x 3384.
4. A few lines in the AGDCDiagnose output have a resolution, such as "SW Src Viewport 5120x2880 @ {0,0}", and they all say 5120x2880. With GC TR, those lines show 6016x3384 for the resolution.

The ae22 variant is for Thunderbolt connection (but not for dual cable 6K).

Both EDID's have the 6K timing.

I see... does that mean that the different EDIDs are coming from the display itself? I was thinking that the Moshi cable was interfering with the EDID, but I guess it makes more sense that the display is somehow detecting the type of cable and selecting an EDID based on that.

Maybe use SwitchResX to see what EDID it is seeing and the list of resolutions. Double click a resolution to show its timing info.

Will do, and will post about it later. But from items 1 through 4 above, it's pretty clear that the Moshi cable is giving me 5K while the GC Titan Ridge gives me 6K.

I'm still dumbfounded that I was not able to reproduce @wago's results with the Moshi cable. No fewer than 4 components of my setup are identical to his.
 

Attachments

  • AGDCDiagnose-Moshi.txt.zip
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I see... does that mean that the different EDIDs are coming from the display itself? I was thinking that the Moshi cable was interfering with the EDID, but I guess it makes more sense that the display is somehow detecting the type of cable and selecting an EDID based on that.
Yes. The display has at least 3 different product IDs (ae22, ae2d, ae2e). Two of them have an override for dual cable connection with two more product IDs (ae22->ae23, ae2e->ae2f). There is an override file for ae21 but I haven't seen that one get used yet. Even a single product ID may have different EDIDs depending on the presets setting.

Will do, and will post about it later. But from items 1 through 4 above, it's pretty clear that the Moshi cable is giving me 5K while the GC Titan Ridge gives me 6K.

I'm still dumbfounded that I was not able to reproduce @wago's results with the Moshi cable. No fewer than 4 components of my setup are identical to his.
Wago was using an earlier version of macOS in April (AGDCDiagnose Version: 4.7.2.2).

I suppose after looking at SwitchResX, you could try to see why the 6016x3384 timings were all rejected. Run the following command in Terminal.app. Disconnect the display. Type Command-K to clear the Terminal.app window. Connect the display. When you see an image, then Select all, Copy, Paste into a text file for review. Search for occurrences of 6016.
log stream --predicate 'sender contains "Thunderbolt" or sender contains "Graphics" or sender contains "Display"' --style compact --info --source

fyi: the following is a list of all the 6016x3384 timings in case you want to try adding one of them to SwitchResX (even though it's probably already in the EDID):
Code:
6016x3384@47.952Hz 210.940kHz 1285.89MHz  h(8 32 40 +)  v(1001 8 6 -)
6016x3384@48.000Hz 210.960kHz 1286.01MHz  h(8 32 40 +)  v(997 8 6 -)
6016x3384@50.000Hz 210.950kHz 1285.95MHz  h(8 32 40 +)  v(821 8 6 -)
6016x3384@59.940Hz 210.928kHz 1285.82MHz  h(8 32 40 +)  v(121 8 6 -)
6016x3384@60.000Hz 210.960kHz 1286.01MHz  h(8 32 40 +)  v(118 8 6 -)
 
Allright, I feel silly now.

It took installing SwitchResX to realize that the solution was in front of me the whole time.

When I ran SwitchResX today (for the first time ever, for me), I saw that it offered 6016 x 3384 in the list of resolutions. I thought, "could it be that simple?". I clicked it, the display went blank, then it came back with everything looking tiny; that's when I noticed that some modes are HiDPI and others are not. So I went to 3008 x 1692 HiDPI, and voila! My Pro Display XDR was in 6K "retina" resolution, looking just the way it does when I connect it directly to the MBP by TB3 - except that I was using the Moshi cable at this time.

To confirm 6K, I ran AGDCDiagnose and found various occurrences of 6016x3384 and no mention of 5120x2880. Strangely, I checked Apple Menu > About this Mac > Displays and it was still showing 5120 x 2880 under Apple Pro Display XDR. But I trust AGDCDiagnose (and my eyes) over About this Mac.

Long story short, the Moshi cable causes the Pro Display XDR to default to 5K. But it's still possible to select 6K by going to System Preferences > Displays > Pro Display XDR > Scaled > click on the far right option (on the left you'll see "Looks like 3008 x 1692"). At this point the monitor goes blank for a while and then comes back, which is a sign that it's really changing the signal to operate with a new resolution.

I don't know why macOS would recognize a Pro Display XDR and default it to 5K. Perhaps there's a technical reason beyond my grasp. And this is Apple, so "you don't need to know". But as I said earlier, when I used a single DP connection from the graphics card to the GC Titan Ridge, and then a TB3 cable from it to the display, it worked at 6K by default. So I don't think there's something missing in the single DP cable setup that would justify making 5K the default resolution.

Now I have the Belkin cable on order, and I'm fairly confident that it will give me 6K with brightness controls.

Thank you @joevt for your time, and for leading me to the solution! Your suggestion of running SwitchResX did it for me. To be honest I was never excited about the idea of running it - I don't even know why. Anyway, all is well now. Perhaps my account of what happened might help some other Pro Display XDR owner out there facing the same issue.
 
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Ok, just dropping by to say that my Belkin cable finally arrived and it works as expected: 6K native resolution on the Pro Display XDR and controls (brightness, presets etc.). I didn't try to use the display's USB ports since I don't need them.

Also I didn't try my LG 5K monitor but this cable would probably give me 4K resolution with the controls.
 
Could you try and see if the usb hub works? I also use the pro xdr on my windows pc with the usb-c port of the 2080ti. (Works
fine with bootcamp drivers force install with profiles and brightness controls and 6k). Now that the virtual link connection is dead. In light of the new nvidia cards. I ordered the belkin cable. Wondering if it works 😀.
 
The USB-c hub works with the Belkin cable. I'm running the (admittedly horrible) link path of:
  1. Mac USB2 => Startech KVM switch
  2. KVM switch => USB hub
  3. USB hub => Belkin cable USB connection
  4. Belkin cable => Pro Display XDR
  5. Pro Display XDR => Logitech 4k USB-C webcam
This all works properly, admittedly at USB2, just because my cable from the Mac to the KVM is still USB2. I need to try USB3, as the KVM supports it. Just haven't had time to recable it.
 
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The USB-c hub works with the Belkin cable. I'm running the (admittedly horrible) link path of:
  1. Mac USB2 => Startech KVM switch
  2. KVM switch => USB hub
  3. USB hub => Belkin cable USB connection
  4. Belkin cable => Pro Display XDR
  5. Pro Display XDR => Logitech 4k USB-C webcam
This all works properly, admittedly at USB2, just because my cable from the Mac to the KVM is still USB2. I need to try USB3, as the KVM supports it. Just haven't had time to recable it.
The Belkin cable is four lanes of HBR2 + USB 2.0. It cannot do USB 3.0. You can look at the USB connector and see that it only has 4 contacts. USB 3.x requires 4 more contacts at least. USB 3.0 without Thunderbolt means two lanes of DisplayPort so that the 2 other lanes can be used for SuperSpeed USB 3.x.

I don't think two lanes of HBR2 is sufficient with the XDR for 6K 60Hz even with DSC. It could be two lanes of HBR3 but that is less bandwidth than four lanes of HBR2. I don't think the XDR does single cable HBR3 (I've not seen anyone get a HBR3 signal through except when it was dual HBR3 over Thunderbolt for 6K without DSC).
 
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Ah nice. That's fine it's for the webcam and logitech mouse / keyboard receiver anyway. No usb 3.0 speeds needed for me. It's nice to swap usb-c cable (pc)/thunderbolt(mbp16) on the display and have everything working.
 
Thanks to this forum I was encouraged to go with the Pro Display XDR and the Radeon Pro W5700 (the non-apple card).
Out of the box on 10.15.6 I got 5k resolution using the thunderbolt cable that came with the monitor directly from the USB-C from the card. While I could select 6k in the display settings the text doesn’t look as crisp and on display info it still shows 5k.
Obviously the USB ports on the back of the display don't work yet and I'm waiting for some cables and adapters, some that were mentioned here, to fix that.
Thank you!
 
Last edited:
Thanks to this forum I was encouraged to go with the Pro Display XDR and the Radeon Pro W5700 (the non-apple card).
Out of the box on 10.15.6 I got 6k resolution using the thunderbolt cable that came with the monitor directly from the USB-C from the card. Obviously the USB ports on the back of the display don't work yet and I'm waiting for some cables and adapters, some that were mentioned here, to fix that.
Does the USB-C port of the W5700 card not work with USB devices? Test with a USB-C to USB-A adapter and a keyboard or mouse. Is there a AMD USB bus in the USB section of System Information.app? Is there a AMD XHC controller in the list of PCI devices in System Information.app?
 
Thank you, the usb c on the back of the display actually work with a flash drive but don’t work with the Logitech 4K magnetic webcam, which is not a big problem as I can plug the camera directly in the computer.
I do have a bigger issue. the computer doesn’t go to sleep. When I try to put it in sleep mode the display turns off but the computer is still on. If I try to wake it it doesn’t wake either. I’m wondering if there’s a firmware that I could update on the blue Radeon W5700. With my old LG monitor the computer sleeps and wakes fine.
If anyone has any suggestions please let me know.
 
Thank you, the usb c on the back of the display actually work with a flash drive but don’t work with the Logitech 4K magnetic webcam, which is not a big problem as I can plug the camera directly in the computer.
I do have a bigger issue. the computer doesn’t go to sleep. When I try to put it in sleep mode the display turns off but the computer is still on. If I try to wake it it doesn’t wake either. I’m wondering if there’s a firmware that I could update on the blue Radeon W5700. With my old LG monitor the computer sleeps and wakes fine.
If anyone has any suggestions please let me know.
While connected to the USB-C port of the W5700, the XDR's USB-C ports can only support USB 2.0. Does the 4K magnetic webcam require USB 3.0? The logitec website says the following:

To enjoy 4K video, the following devices require direct connection between webcam and device, using the 4K Pro Magnetic Webcam Extension Cable (included in the box):​
  • MacBook® 13" (2018 or later) while connected to eGPU
  • MacBook Pro 15" (2018 or later)
  • iMac® (2019)
  • Mac Pro® (2019)

The faq says:

Then, to stream and record video up to 4k in 30fps or 1080HD in 60fps, make sure you're using a USB 3.1 cable. With a USB 2.0 cable, the best video quality you can have is 1080HD, 30fps.​

To ensure you will be able to record video up to 4K at 30 frames per second or 1080p at 60 frames per second (fps), you must use a USB 3.1 cable. If you use a USB 2.0 cable, the maximum definition and frame rate of the video will be limited to 1080p at 30 fps.​
To enjoy 4K video, you only need to use the extended 6 foot / 182.9 cm cable if you are using one of these devices:​
  • MacBook® 13" (2018 or later) while connected to eGPU
  • MacBook Pro 15" (2018 or later)
  • iMac® (2019)
  • Mac Pro® (2019)
For the sleep issue, maybe the system log has messages about what is causing the sleep or wake to fail. Maybe there's a thread that talks about generic sleep issues.


 
While connected to the USB-C port of the W5700, the XDR's USB-C ports can only support USB 2.0. Does the 4K magnetic webcam require USB 3.0? The logitec website says the following:

To enjoy 4K video, the following devices require direct connection between webcam and device, using the 4K Pro Magnetic Webcam Extension Cable (included in the box):​
  • MacBook® 13" (2018 or later) while connected to eGPU
  • MacBook Pro 15" (2018 or later)
  • iMac® (2019)
  • Mac Pro® (2019)

The faq says:

Then, to stream and record video up to 4k in 30fps or 1080HD in 60fps, make sure you're using a USB 3.1 cable. With a USB 2.0 cable, the best video quality you can have is 1080HD, 30fps.​

To ensure you will be able to record video up to 4K at 30 frames per second or 1080p at 60 frames per second (fps), you must use a USB 3.1 cable. If you use a USB 2.0 cable, the maximum definition and frame rate of the video will be limited to 1080p at 30 fps.​
To enjoy 4K video, you only need to use the extended 6 foot / 182.9 cm cable if you are using one of these devices:​
  • MacBook® 13" (2018 or later) while connected to eGPU
  • MacBook Pro 15" (2018 or later)
  • iMac® (2019)
  • Mac Pro® (2019)
For the sleep issue, maybe the system log has messages about what is causing the sleep or wake to fail. Maybe there's a thread that talks about generic sleep issues.




SOLVED, IT WORKS!!



In case this is helpful to anyone:



Sleep works after connecting the Pro Display XDR directly to the thunderbolt on the motherboard Gigabyte Z490 vision D.

I had to enable all items under the thunderbolt in bios to get it to work. And it works both in Catalina 10.15.6 and Big Sur latest beta as of this post.

Just using a random mini display to display cable (it may be the cable that came with the graphics card, don’t even remember) to feed the thunderbolt port on the motherboard from the Radeon Pro W5700.
This is the only way to get 6k on my system. I was wrong in my previous post when I said that 6k worked directly from the W5700 card.

In the process, I updated the firmware of the Pro Display. I had to do what Apple said here to be able to receive the update. Took about 15 min and couple of restarts to get the update notification from Apple.
For the firmware update to download, make sure “Install system data files and security updates” and “Install macOS updates” are selected in the Advanced window of Software Update preferences.


The Logitech webcam now works plugged directly in the display. Now I get USB 3 speeds from the display (around 400 mbps measured with Blackmagic Disk app).



For anyone interested in this build see here:




Many thanks to Joevt who replied during my anguish and to all who contributed to this thread!
 
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@gimarbazat That's amazing.

Just to clarify, you connected the W5700's miniDP port to DP-IN on the motherboard using a Display Port 1.4 cable? And then you connected a Mosh usb-C thunderbolt cable from one of the motherboard TB3 ports to the Pro Display?

Could you please also confirm 60hz or 30Hz refresh rate @ 6K?

I am thinking of purchasing Pro Display XDR and I have the exact same config (10900K + Gigabyte Z490 Vision D). Just want to confirm everything 100% before I drop $5k on a display :)

Thank you!
 
@gimarbazat That's amazing.

Just to clarify, you connected the W5700's miniDP port to DP-IN on the motherboard using a Display Port 1.4 cable? And then you connected a Mosh usb-C thunderbolt cable from one of the motherboard TB3 ports to the Pro Display?

Could you please also confirm 60hz or 30Hz refresh rate @ 6K?

I am thinking of purchasing Pro Display XDR and I have the exact same config (10900K + Gigabyte Z490 Vision D). Just want to confirm everything 100% before I drop $5k on a display :)

Thank you!

Exactly, I used this $7 cable from the link below to connect the W5700 to the DP-IN on the motherboard. From the motherboard to the monitor I'm using Apple's thunderbolt cable that came with the monitor. SwitchResX says 3008x1692 HiDPI @ 60hz. Everything looks great and sharp. Under Graphics/Displays in System Report it shows 6016 x 3384 Retina 6K. Presets all work. It's the most freakin' amazing monitor I've owned.
https://www.amazon.com/dp/B0786FNLDT/ref=cm_sw_em_r_mt_dp_QcfBFbA9MNQWQ

Use the EFI from Chris and choose the default config file with the iMac Pro SMbios.
Use the same settings in BIOS as Chris but enable everything under Thunderbolt (including thunderbolt boot or something like that) to get this working 100% with sleep and profiles after restart, and to get USB 3 speed for the hub on the back of the display.
If you need any other help let me know.

I'm about to try it with an inexpensive RX 580 tomorrow to see whether the monitor still works and I'll post.
 
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I'm about to try it with an inexpensive RX 580 tomorrow to see whether the monitor still works and I'll post.
It should work, but only up to 4K since the RX580 doesn't support DSC. Your motherboard would need to DisplayPort inputs to support 6K and even then the Thunderbolt controller might not have the firmware to support dual HBR3 connection to the XDR for 6K.

6K 60Hz requires ~1290 MHz pixel clock. We know that the XDR does not support chroma sub sampling. If macOS supported 6 bpc, then 6K 60Hz could work with a single HBR3 connection, but I don't think I've ever seen anyone get a single HBR3 connection to work. In that case, you'll be limited to single HBR2 connection. One person got 5K 60Hz with 6 bpc in Windows. Does AMD support 6 bpc in Windows?

If you want 6K with single HBR2 connection, then you can try making a custom timing (CVT-RB) in SwitchResX (I don't think anyone has tried lower refresh rates before):
6K 30 Hz 8 bpc (635.81 MHz).

While you're testing the XDR with different connection types, can you gather some info about the different connection methods of the USB hub of the XDR?
#126
 
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