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Oh, this is very helpful!

That is, if monitors 1 and 2 are connected to the ports of the rear I/O Card ports thunderbolt (mpx module 580x will be the controller of these ports), and monitor 3 is connected by hdmi to the rx6900xt card, and is assigned as the main one in the system settings, then the main video card will be rx6900xt?

Do you use programs like iStat Menu? Tell me, does it reflect the statistics of the rx6900xt GPU, video memory, and also the temperature?
Yes, that is what is reported once the Mac OS is fully booted up and running.

I do have iStat Menus as well as iStatistica Pro. Both are reporting the GPU stats.

Screenshot 2023-08-09 at 10.25.28 AM.png
 
Yes, that is what is reported once the Mac OS is fully booted up and running.

I do have iStat Menus as well as iStatistica Pro. Both are reporting the GPU stats.
Thanks again, thanks to your comments, I decided to buy rx6900xt and it works great on the main monitor, while 580 draws pixels for two peripheral monitors)) it's a dream!
 
Question…

I have a Gigabyte 6900XT which requires 3x power cables.

I want to add another 6900XT… how?! Can I daisy chain the cables somehow?
 
I had purchased 2 RX 6900XT cards a few years back for my 7,1. I used slots 1 & 3. I never could get the OS to use the 2nd card, though the system would identify a 6900XT in that slot. It would show up as a 6900 in slot 3, but any monitor plugged into the card wouldn’t produce a signal. It just kinda sat there idle. I ran both monitors off the card in slot 1 and gave up after a whole bunch of experimentation. The card never felt properly seated or locked down in slot 3 either, it did power on— couldn’t tell if it was something in the OS or a physical slot issue.

I’d been clicking along just fine. The card worked great. Once in a while it would go to a black screen when gaming. Only a reboot would bring it back. Working theory is that the card overheated and would shut down.

This week I started a Resolve project in 4k. I normally cut in 1080, but this is a special project. Everything was fine— then after a full day of editing the screen black issue returned. No amount of reboots would bring the monitors back online. Assuming overheating again. I swapped the 2nd card in— just in case the card in slot 1 was bad, but it experienced the same issue, screen black.

I put the old VEGA II in slot 1 and everything has been fine since. I’d love to put two WRX6900 MPX or WRX6800 cards in— but it’s pretty ridiculous to drop upwards of $3k on a 7,1 when Apple silicon is outpacing that machine. Best outcome would be to find out I need a driver or some software to get the RX 6900 XT to work properly. Love the I/O on the 7,1, just hoping to figure out what can be done here. Thanks in advance you wizards!
 
I had purchased 2 RX 6900XT cards a few years back for my 7,1. I used slots 1 & 3. I never could get the OS to use the 2nd card, though the system would identify a 6900XT in that slot. It would show up as a 6900 in slot 3, but any monitor plugged into the card wouldn’t produce a signal. It just kinda sat there idle. I ran both monitors off the card in slot 1 and gave up after a whole bunch of experimentation. The card never felt properly seated or locked down in slot 3 either, it did power on— couldn’t tell if it was something in the OS or a physical slot issue.

What happened with only the slot 3 card installed, and displays plugged in to it?
 
What happened with only the slot 3 card installed, and displays plugged in to it?
I couldn't remember-- as it was several years ago-- but I just checked. It took a couple of tries, but the 6900 xt card works in slot 3, as long as slot 1 doesn't have a card. Maybe putting distance between the PSU and the 6900 will keep it cooler? Still doesn't explain why I can't run both. Mystery of mysteries-- this system should scream if I could get 2 cards running.
 
I run a 6900XT in slot 3 in my MP7.1 without any problems.
I did too, out of slot 1 for several years. It's recently that I've been getting the screen black issue. On each occasion I was doing something more GPU-intense (Running Resolve with a 4k timeline, etc.) I've not had the issue repeat since moving to slot 3. Would love to figure out why I can't put one monitor on each 6900 and split the load. I'll be opening the computer up again this week-- I'm putting some additional RAM in it. I'll experiment more and see if I can't add that 2nd card again.
 
I run a 6900XT in slot 3 in my MP7.1 without any problems.
What happened with only the slot 3 card installed, and displays plugged in to it?
Success! I tried the 6900 in both slots again-- but this time the slot 3 card would be showing video while the slot 1 card would not. That didn't make any sense. So I pulled the power cables on slot 1 and went through them with a multimeter. One of the female pins had pushed back into the cable housing. I pressed the wire back into the connector, hooked it up and -- it's working. Cards in slots 1 and 3, each connected to a separate monitor. Thanks for your help everyone. We jammin'.
 
Success! I tried the 6900 in both slots again-- but this time the slot 3 card would be showing video while the slot 1 card would not. That didn't make any sense. So I pulled the power cables on slot 1 and went through them with a multimeter. One of the female pins had pushed back into the cable housing. I pressed the wire back into the connector, hooked it up and -- it's working. Cards in slots 1 and 3, each connected to a separate monitor. Thanks for your help everyone. We jammin'.

It's always the thing you should check first, that you end up checking last. 😅
 
It's always the thing you should check first, that you end up checking last. 😅
I didn't think to check the cables because both cards were lit and spinning. They were visually getting power and showing up to the OS, I'd see 6900, both cards would ID, but only one would work. Who knew?
 
Update: The system worked great for 24 hours, then the Slot 3 card failed again. My suspicion was immediately the power cables again, so I ordered a new set from OWC. The system has been running for a full day now with no issues. Fingers crossed, I just had been working with a bad batch of cables.

Posting this to help others who are experiencing similar issues with 2 non-MPX graphics cards. Look to the power cables early during troubleshooting.

One other note: the 6900xt sags badly in slot 3. I bought a neat card supporter expandable bolt for $6 off Amazon to wedge between the two cards on the floppy end. I don't know if it was causing any issues, but giving the card in slot 3 some support didn't seem like a bad idea. https://www.amazon.com/dp/B0D35DGN7T?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
 
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One other note: the 6900xt sags badly in slot 3. I bought a neat card supporter expandable bolt for $6 off Amazon to wedge between the two cards on the floppy end. I don't know if it was causing any issues, but giving the card in slot 3 some support didn't seem like a bad idea. https://www.amazon.com/dp/B0D35DGN7T?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

It's a shame there isn't a universal bracket that can be fitted to a normal card, which engages with the MPX latch mechanism.
 
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Not sure what requesting the similar screenshot will reveal to you minus the missing Brightness/True Tone box. That's all you're not seeing.

Here, I'll do one better. Screenshots of what you're requesting and detailed information of how it's connected in both Mac OS and Windows 10 Boot Camp.View attachment 2161883View attachment 2161882View attachment 2161870View attachment 2161873View attachment 2161874
RX 6900 XT & High Refresh 4K: Can it push beyond 100Hz?
Hey all, trying to max out my 4K setup. My monitors do 144Hz and 165Hz, but I'm seeing info suggesting a 100Hz cap for the 6900 XT. Can anyone confirm the actual max frame rate this card supports at 4K? Does anyone have a model that reliably hits 120Hz, 144Hz, or higher? What cable/port setup are you using?
 
RX 6900 XT & High Refresh 4K: Can it push beyond 100Hz?
Hey all, trying to max out my 4K setup. My monitors do 144Hz and 165Hz, but I'm seeing info suggesting a 100Hz cap for the 6900 XT. Can anyone confirm the actual max frame rate this card supports at 4K? Does anyone have a model that reliably hits 120Hz, 144Hz, or higher? What cable/port setup are you using?

Why wouldn't it hit 120/144hz? It is an older card, but it still performs well.
 
Why wouldn't it hit 120/144hz? It is an older card, but it still performs well.
Hey SDAVE, thanks for the reply!

My question was specifically about macOS limitations on the Mac Pro 7.1, inspired by the original post in this thread. As you can see from the OP's screenshots, the same monitor runs at 144Hz in Windows but is capped at 100Hz in macOS — despite using the same hardware.

This mirrors my own experience:
I’m currently using the Radeon Pro 580X MPX in my Mac Pro. Technically, it supports DisplayPort 1.4 (capable of 4K@144Hz via DSC), yet macOS only offers me 60Hz max on my 4K monitors (both HDMI 2.0 and DP).

So while the RX 6900 XT undoubtedly can push 120Hz+/4K on Windows (as the OP’s screenshots prove), my concern is whether macOS will actually unlock those refresh rates on a Mac Pro 7.1. If the OS is imposing a 100Hz cap (as seen in the OP’s case), upgrading the GPU might not help.

Before investing in a 6900 XT, I’m trying to confirm:
Has anyone with a Mac Pro 7.1 + RX 6900 XT combo successfully achieved 4K@120Hz, 144Hz, or 165Hz in macOS? Or any other GPU?
 
Hey SDAVE, thanks for the reply!

My question was specifically about macOS limitations on the Mac Pro 7.1, inspired by the original post in this thread. As you can see from the OP's screenshots, the same monitor runs at 144Hz in Windows but is capped at 100Hz in macOS — despite using the same hardware.

This mirrors my own experience:
I’m currently using the Radeon Pro 580X MPX in my Mac Pro. Technically, it supports DisplayPort 1.4 (capable of 4K@144Hz via DSC), yet macOS only offers me 60Hz max on my 4K monitors (both HDMI 2.0 and DP).

So while the RX 6900 XT undoubtedly can push 120Hz+/4K on Windows (as the OP’s screenshots prove), my concern is whether macOS will actually unlock those refresh rates on a Mac Pro 7.1. If the OS is imposing a 100Hz cap (as seen in the OP’s case), upgrading the GPU might not help.

Before investing in a 6900 XT, I’m trying to confirm:
Has anyone with a Mac Pro 7.1 + RX 6900 XT combo successfully achieved 4K@120Hz, 144Hz, or 165Hz in macOS? Or any other GPU?

The 580x MPX is only connecting to displayport via Thunderbolt 3. Thunderbolt 3 only supports DP 1.2. I'd suspect that's your bottleneck.
 
Hi mattspace,
Just to clarify: Thunderbolt 3 does support DisplayPort 1.4 via Alt Mode (source).
My MacBook Pro 16" (2019, Radeon 5600M, TB3) drives the same 4K monitor at 144Hz without issues.

Core question remains:
Has anyone with a Mac Pro 7.1 (regardless of GPU – 6900 XT, W6800, etc.) personally achieved 4K @ 120/144/165Hz in macOS?
 
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