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ChromeCrescendo

macrumors 6502
Original poster
Jan 3, 2020
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I have the XDR with the W5700X graphics card and wondering if the USB ports on the XDR will take advantage of USB 3.2 speeds or only 3.0?

Thank you and be well.
 

joevt

Contributor
Jun 21, 2012
6,761
4,100
USB 3.0 (5 Gbps). The XDR has an internal USB 3.0 hub to provide more than one USB 3.0 port.

I've never seen Apple or any display manufacturer use a USB 3.1 Gen 2 (10 Gbps) USB hub.

I don't know if macOS can handle USB 3.2 Gen 2x2 (20 Gbps) USB.
 

nicho

macrumors 601
Feb 15, 2008
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3,211
USB 3.0 (5 Gbps). The XDR has an internal USB 3.0 hub to provide more than one USB 3.0 port.

I've never seen Apple or any display manufacturer use a USB 3.1 Gen 2 (10 Gbps) USB hub.

I don't know if macOS can handle USB 3.2 Gen 2x2 (20 Gbps) USB.

This is not the case, according to Apple:


They are USB2 ports unless connected to a 16-inch MBP, when they work as USB 3.1 Gen 1 (5Gbps, = USB 3.0) ports.
 

joevt

Contributor
Jun 21, 2012
6,761
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This is not the case, according to Apple:


They are USB2 ports unless connected to a 16-inch MBP, when they work as USB 3.1 Gen 1 (5Gbps, = USB 3.0) ports.
I don't think what I said disagrees with Apple. The original poster is talking about a W5700X which has Thunderbolt and supports DSC so he should get USB 3.0. The Apple tech specs for the XDR were written before the W5700X became available. It would be super strange if only the MacBook Pro 16 inch could use the ports as USB 3.0.

They are USB 3.0 ports in the following situations:
1) The display is connected with Thunderbolt 3 to a computer that has a Thunderbolt bus with a DisplayPort 1.4 connection to a AMD Navi GPU, Nvidia RTX, or Intel Ice Lake GPU, that supports DSC.
2) The display is connected with Thunderbolt 3 to a computer that has a Thunderbolt bus with only one DisplayPort signal.
3) The display is connected with Thunderbolt 3 to a computer that has a GPU that only supports DisplayPort 1.2.

They are USB 2.0 ports in the following situations:
4) The display is connected with a USB-C cable to a computer that does not have Thunderbolt (either a USB-C port or a DisplayPort port and USB 2.0 port using the BELKIN CHARGE AND SYNC CABLE FOR HUAWEI VR GLASS).
5) The display is connected with Thunderbolt 3 to a Mac or Blackmagic eGPU that has a Thunderbolt bus with two DisplayPort 1.4 connections to a GPU that does not support DSC.

#1 is the situation you are talking about (MacBook Pro with 5300M or 5500M) but there are other ways to achieve #1 (iMac 2020 with 5700XT, MacBook Air 2020, MacBook Pro 2020 13 inch with 10th generation CPU, or Navi or RTX GPU connected to a GC-TITAN RIDGE).
For #4, all four super speed lanes are used for DisplayPort leaving only USB 2.0 lines for USB.

I would like to see some ioreg -lw0 output as evidence for situation #2, #3, and #5 because I'm not 100% sure of those (maybe for situation #1 also to satisfy the XDR tech specs question ).
With #2 and #3, one DisplayPort 1.4 signal or two DisplayPort 1.2 signals leaves enough bandwidth for USB 3.0 but Apple could do something silly and force USB 2.0? I don't think I've seen the XDR with a single HBR3 signal so single and dual HBR2 will probably be all the situations that can be tested (use AGDCDiagnose to view the current connection types to a display).
With #5, there is not enough bandwidth for USB 3.0 but the USB controller could be USB 3.0 with reduced PCIe bandwidth which could perform slightly better than USB 2.0?
 
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nicho

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Feb 15, 2008
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I don't think what I said disagrees with Apple. The original poster is talking about a W5700X which has Thunderbolt and supports DSC so he should get USB 3.0. The Apple tech specs for the XDR were written before the W5700X became available. It would be super strange if only the MacBook Pro 16 inch could use the ports as USB 3.0.

It would also be super strange if Apple didn't update their technical specs for a product they currently sell to reflect that ¾ of their laptops are capable of getting USB 3 speeds out of the box (along with certain configurations of their desktops) while at the same time adding them to the "compatibility" list on the same page.
 

joevt

Contributor
Jun 21, 2012
6,761
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It would also be super strange if Apple didn't update their technical specs for a product they currently sell to reflect that ¾ of their laptops are capable of getting USB 3 speeds out of the box (along with certain configurations of their desktops) while at the same time adding them to the "compatibility" list on the same page.
Right. If the models from the compatibility list marked #1 below do support USB 3.0 as I guess, then the specs need fixing. I could be wrong.
  • Mac Pro (2019) with MPX Module GPUs : #1 for W5500X and W5700X, #5 for 580X, Vega II, Vega II Duo
  • 15-inch MacBook Pro (2018 or later) #5
  • 16-inch MacBook Pro (2019) #1
  • 21.5-inch iMac (2019) #5
  • 27-inch iMac (2019 or later) #5
  • MacBook Air (2020) #1
  • 13-inch MacBook Pro with four Thunderbolt 3 ports (2020) #1
  • Any Mac model with Thunderbolt 3 ports paired with Blackmagic eGPU or Blackmagic eGPU Pro #5
The specs have been known to be inaccurate - for the Vega II, it says you can connect two XDR displays, but people have been able to connect three and get 6K 60Hz from each. The Use multiple displays with your Mac Pro (2019) page says you can only connect two XDR to the Vega II Duo but the Use the Radeon Pro Vega II Duo MPX Module with your Mac Pro page says you can connect 4.

The Mac Pro 2019 tech specs says the W5700X supports DSC but does not mention that for W5500X.

If the W5500X and W5700X support DSC, then you should be able to connect two XDR displays to a single bus but Apple says to use one display per bus. With DSC, you can connect 6 XDR displays to the W5700X or two XDR displays to the W5500X and each one gets a HBR2 with DSC signal, but maybe the GPU doesn't like to drive that many pixels at 60 Hz with compression?

Maybe a GPU supports DSC but able disables it in certain situations? I believe there is a flag in the display overrides to do that.
 

nicho

macrumors 601
Feb 15, 2008
4,222
3,211
Right. If the models from the compatibility list marked #1 below do support USB 3.0 as I guess, then the specs need fixing. I could be wrong.
  • Mac Pro (2019) with MPX Module GPUs : #1 for W5500X and W5700X, #5 for 580X, Vega II, Vega II Duo
  • 15-inch MacBook Pro (2018 or later) #5
  • 16-inch MacBook Pro (2019) #1
  • 21.5-inch iMac (2019) #5
  • 27-inch iMac (2019 or later) #5
  • MacBook Air (2020) #1
  • 13-inch MacBook Pro with four Thunderbolt 3 ports (2020) #1
  • Any Mac model with Thunderbolt 3 ports paired with Blackmagic eGPU or Blackmagic eGPU Pro #5
The specs have been known to be inaccurate - for the Vega II, it says you can connect two XDR displays, but people have been able to connect three and get 6K 60Hz from each. The Use multiple displays with your Mac Pro (2019) page says you can only connect two XDR to the Vega II Duo but the Use the Radeon Pro Vega II Duo MPX Module with your Mac Pro page says you can connect 4.

The Mac Pro 2019 tech specs says the W5700X supports DSC but does not mention that for W5500X.

If the W5500X and W5700X support DSC, then you should be able to connect two XDR displays to a single bus but Apple says to use one display per bus. With DSC, you can connect 6 XDR displays to the W5700X or two XDR displays to the W5500X and each one gets a HBR2 with DSC signal, but maybe the GPU doesn't like to drive that many pixels at 60 Hz with compression?

Maybe a GPU supports DSC but able disables it in certain situations? I believe there is a flag in the display overrides to do that.

The difference between those examples of inaccuracies and this is that if you are correct then they are on the same page and therefore it isn't a case of one piece of information being older than the other.

USB 2 speeds aren't exactly something to shout about in 2020, so you'd think Apple would highlight every device that is the exception.
 
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