The ultimate Pro Display XDR info thread

[joevt]

Is there a way I can determine if DSC is enabled for my XDR? I have a 2019 Mac Pro with the W5700X, but the machine and the XDR are far enough apart that I can't quite get the display plugged directly into the GPU - instead it's connected to one of the TB3 ports on the Apple IO card in the top PCIe slot.
I'm using a TS3+ as essentially a TB3 extender for a second display (LG UltraFine 5K), but I didn't think that was possible for the XDR because of its bandwidth requirements. This thread seems to suggest that if I put a second TS3+ under my desk, I could get the extra length I need to connect to the GPU directly and have DSC enabled.

The output from the AGDCDiagnose command will tell you if DSC is enabled.
If you have a 5 Gbps USB device and you can write to it at 400 MB/s while it's connected to the XDR running at 6K, then the XDR is probably using DSC.
If you connect the XDR to the TS3+ and it still works at 6K then it's probably using DSC.
If the XDR is not using DSC and it is running at 6K, then you won't be able to connect another display to the same Thunderbolt controller.

 

[cmsj]

The output from the AGDCDiagnose command will tell you if DSC is enabled.
If you have a 5 Gbps USB device and you can write to it at 400 MB/s while it's connected to the XDR running at 6K, then the XDR is probably using DSC.
If you connect the XDR to the TS3+ and it still works at 6K then it's probably using DSC.
If the XDR is not using DSC and it is running at 6K, then you won't be able to connect another display to the same Thunderbolt controller.

Thanks. I had a look at the AGDCDiagnose output and I think it's saying the XDR is getting two DP streams, only one of which has DSC enabled?

I pasted it here: https://pastebin.com/uzxXjWUJ

 

[joevt]

Thanks. I had a look at the AGDCDiagnose output and I think it's saying the XDR is getting two DP streams, only one of which has DSC enabled?

I pasted it here: https://pastebin.com/uzxXjWUJ

None of the four connections have DSC Enabled.
The first two are for each half of the XDR. The last two are for each half of the 5K.
I'm not sure why it's choosing to use dual link SST instead of DSC. Maybe try disconnecting the 5K? Try any of the 7 other Thunderbolt ports. Try connecting a 5 GB/s SSD. Try connecting the XDR to the TS3+.

It looks like the XDR connected as HBR+HBR3 (because that's the normal limit of Thunderbolt) and then macOS forces it to HBR3+HBR3 (because that's what's needed for a dual link SST 6K and 3008x3384 doesn't require all the HBR3 bandwidth and Thunderbolt doesn't transmit DisplayPort stuffing symbols that are used to fill the DisplayPort link bandwidth).
For 6K with DSC, only one HBR2 connection is required. You could force a HBR2 connection using a USB-C (not Thunderbolt) cable but then the USB would be limited to USB 2.0. But I don't know if you would get DSC or if you would be limited to 4K.

If you were running Catalina, then you might get DSC.

 

[cmsj]

None of the four connections have DSC Enabled.
The first two are for each half of the XDR. The last two are for each half of the 5K.
I'm not sure why it's choosing to use dual link SST instead of DSC. Maybe try disconnecting the 5K? Try any of the 7 other Thunderbolt ports. Try connecting a 5 GB/s SSD. Try connecting the XDR to the TS3+.

It looks like the XDR connected as HBR+HBR3 (because that's the normal limit of Thunderbolt) and then macOS forces it to HBR3+HBR3 (because that's what's needed for a dual link SST 6K and 3008x3384 doesn't require all the HBR3 bandwidth and Thunderbolt doesn't transmit DisplayPort stuffing symbols that are used to fill the DisplayPort link bandwidth).
For 6K with DSC, only one HBR2 connection is required. You could force a HBR2 connection using a USB-C (not Thunderbolt) cable but then the USB would be limited to USB 2.0. But I don't know if you would get DSC or if you would be limited to 4K.

If you were running Catalina, then you might get DSC.

So I tried connecting the XDR via the TS3+ and it does seem like it works: https://pastebin.com/mbUTJHqU

I'm able to set the full 6K resolution, have the P3-1600 nit colour preset and also (not that it should matter since this is a GPU-side scaling thing) force an 8K mode.

This is very exciting, although it now means that to retain DSC I either need to buy a second TS3+ to extend the LG 5K's TB3 cable, or spend even more than that on a 5m optical TB3 cable, or I guess run the LG over a 5m USB-C cable.

Edit: Hmm, I've previously seen people struggling to get the XDR fully working over optical TB3 cables, but with DSC does this now mean that you could actually run both the full 6K and USB3 over one of Corning's cables?

Thanks @joevt, your expertise here is greatly appreciated!

 

[joevt]

So I tried connecting the XDR via the TS3+ and it does seem like it works: https://pastebin.com/mbUTJHqU

I'm able to set the full 6K resolution, have the P3-1600 nit colour preset and also (not that it should matter since this is a GPU-side scaling thing) force an 8K mode.

Yup, your 2nd AGDCDiagnose says the XDR connected using 4 lanes of HBR2 using DSC@12bpp (decompresses to RGB 12bpc HDR10) with pixel clock 1286.01 MHz.
Your 1st AGDCDiagnose shows the XDR connected using two 4-lane HBR3 connections RGB 10bpc HDR10. It doesn't show the timing info of each connection (pixel clock 648.91MHz). Instead, it shows the fake full 6K timing info from the mtdd overlay (pixel clock 1286.01 MHz).

This is very exciting, although it now means that to retain DSC I either need to buy a second TS3+ to extend the LG 5K's TB3 cable, or spend even more than that on a 5m optical TB3 cable, or I guess run the LG over a 5m USB-C cable.

LG UltraFine 5K requires a 40 Gbps cable for 5K because it does not support DSC (it uses two 4-lane HBR2 connections for RGB 10bpc).

Edit: Hmm, I've previously seen people struggling to get the XDR fully working over optical TB3 cables, but with DSC does this now mean that you could actually run both the full 6K and USB3 over one of Corning's cables?

If the XDR will connect with DSC over the optical 40Gbps cable then its hub will have USB 3.0 speed. Actually, 6K60 12bpp (DSC) only requires 1286.01 MHz * 12 bpp = 15.4 Gbps so you can get full or near full USB 3.0 speed (4Gbps) with a 20 Gbps cable as long as the connection uses Thunderbolt instead of DisplayPort Alt Mode.

I'm still not understanding why it didn't connect with DSC in your first test. Maybe Apple prefers to give you an uncompressed video signal instead of a DSC signal?
If you connected a 5 Gbps USB device, would they prefer uncompressed video + USB 2.0 speed over DSC compressed video + USB 3.0 speed?

 

[atefsh]

Hi,

I'd like to know how much the shipping box with the display and stands weighs and the box's dimension.

That's all.

Thanks.