Mac Studio M2 max struggling to drive 5K / 5120x1440 ultra-wide monitor

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Level 2

441 points

Mac Studio M2 max struggling to drive 5K / 5120x1440 ultra-wide monitor

I have a Mac Studio M2 Max and a 5120x1440 monitor and the Mac Studio really isn't able to drive the monitor. Has anyone else had this problem?

Basically it reverts to half-resolution whenever I restart... and only recovers when I change thunderbolt ports after booting and logging in... and only then if there are no other peripherals attached to the computer... not even ethernet connected to the built-in 10GbaseT port.

Here's more detail on the symptoms:

Problem #1:

If I power off, unplug literally everything from the Mac Studio except the monitor (directly connected via a Thunderbolt 4 cable), and then press the power button, the computer will boot and send 2560x1440 to the monitor (resulting in either badly stretched image or only rendering on the middle half of the screen). The higher resolutions are not listed as options in Settings>Displays (even if I check "show all resolutions).
If I log in and then hot-swap the monitor cable to a different port on the back of the Mac Studio, I miraculously recover full resolution. (Note: it doesn't matter which port -- if I start in port 1 and move to port 2, great; if I start in port 2 and move to port 1, great; if I start in port 1, unplug, and re-plug into port 1, no good.) The monitor auto switches to full 5120x1440 and MANY more higher-than-2560x1440 options appear in the settings list.

Problem #2

If I plug in an ethernet cable into the computer's native port (connected to a 10GbaseT switch) and repeat the steps above then no amount of swapping monitor ports seems to restore full resolution. So basically, the Mac Studio cannot use the 10G ethernet Apple charged me for and the 5K advertised supported resolution simultaneously(!)
If I unplug ethernet and plug in a thunderbolt-2 based external hard drive enclosure (operating at 10Gbps via an apple-brand3ed Thunderbolt 2-to-Thunderbolt 4 adapter), things work as described in Problem #1 above.
If I unplug the hard drive enclosure and ethernet but plug in a USB3 gen 2 hub with a few printers and a scanner attached to it, then same behavior as ethernet. (Note that if I plug any of these devices in *after* restoring resolution, then full resolution persists and the devices *seem* to work -- though I haven't run exhaustive speed tests.)

Other misc. notes:

Mac Studio 2023 w/ Apple M2 Max 32GB RAM. Running Sequoia 15.3.1.
Monitor is an Innocn 49C1R, running at 60Hz.
Using a 79" OWC Thunderbolt 4 cable. (I tried swapping to an (obscenely expensive) Apple-branded 3m Thunderbolt 4 cable and this didn't improve things. However FWIW, I believe that hot swapping the cable in the SAME port will restore full resolution.)
I've tried safe mode; doesn't solve things.
I've tried deleting com.apple.windowserver.displays.plist (from preferences folders in both /Library and ~/Library) and restarting; doesn't solve things.
AppleCare support now mainly wants to wipe and reinstall the operating system (presumably because that's a generic troubleshooting step that is easy for them but very disruptive for me). Note that this problem has persisted through several OS version upgrades.
I can't get any good information from apple on either (i) how/when the OS polls the monitor to determine supported resolutions (though presumably changing ports triggers this), (ii) how the Thunderbolt bus allocates bandwidth between devices (other than a generic comment that it "prioritizes displays"), or (iii) which busses compete for bandwidth (e.g., does the built-in ethernet port compete with the thunderbolt ports for the 40GBps capacity or is it additive? One apple support person said yes another said no.)

Either way it *seems* like something is wrong in Mac OS and/or the Mac Studio's thunderbolt bus...

Does anyone have any advice?

Many thanks!

-Mike

Mac Studio, macOS 15.3

Posted on Feb 25, 2025 6:31 PM

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Answer 1

den.thed

Level 10

84,550 points

Feb 25, 2025 8:22 PM in response to Mike G.

I would test that display on a short 3.3ft TB4/3 USB-C to DisplayPort 1.4 8K cable.

for example: > https://www.amazon.com/gp/aw/d/B0BXLDJV3Y/?th=1

Then if the TB4/3 USB-C to DisplayPort cable doesn't fix, I would move to the Apple Thunderbolt 4 Pro cable.

https://www.apple.com/shop/product/MW5J3AM/A/thunderbolt-4-usb%E2%80%91c-pro-cable-18-m?

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Answer 2

Mike G. Author

Level 2

441 points

Feb 28, 2025 12:57 PM in response to Grant Bennet-Alder

Thanks. But now that i look at it, the specs for the Mac Studio (Mac Studio - Technical Specifications - Apple) suggest that nothing above 4K is supported over HDMI regardless of the cable. (I can’t tell whether a thunderbolt-at-one-end-HDMI-at-the-other cable/adapter would be subject to the Thunderbolt limit or the HDMI limit, though…)

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Answer 3

Mike G. Author

Level 2

441 points

Feb 28, 2025 9:39 AM in response to Grant Bennet-Alder

Thanks for this! Trying to unpack it all and figure out what I should *do* about it:

It looks like you're correct: the monitor is actually USB-C rather than thunderbolt. Given that the monitor advertises this resolution, should I be using a different connection (e.g., HDMI or DisplayPort)? Or is that a shady advertisement on the part of the monitor company?
The only options Mac OS offers for refresh rate on this monitor are 60hz and 120hz.
Unfortunately the cable needs to be longer than 1m (it's on a mount and even if it weren't the location of the port on the monitor and the loctcation of the port on the Mac mini together with the bend radius of a heavy cable make it nearly impossible to place the computer anywhere that a 1m cable would suffice.) If I could somehow shoehorn the computer sideways next to the monitor and use a 1m USB-C cable, are you saying you think this would miraculously solve my problems?

(FWIW, I've also noticed that the expensive apple cable only works occasionally -- It's the behavior I describe as "problem #1" except whereas the OWC cable reverts to half resolution until the port is swapped, the apple cable gives me blank screen most of the time...)

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Answer 4

Feb 28, 2025 2:12 PM in response to Mike G.

from that document:

HDMI display video output

Support for one display with up to 8K resolution at 60Hz or 4K resolution at 240Hz
Support for variable refresh rate (VRR), HDR, and multichannel audio

Use the DIRECT HDMI output. Apple does Not recommend the use of adapters when connecting high-end HDMI devices, for good reasons.

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Answer 5

Feb 25, 2025 7:06 PM in response to Mike G.

that display appears to be a short 5K display -- that is, the data rates must be supported for its 5k width, but the bottom half of a full 5K display are absent.

interfaces appear to include USB-C, NOT Thunderbolt.

<<Using a 79" OWC Thunderbolt 4 cable. >>

that cable is too long to run a display at high data rates.

the limit for an ordinary passive USB-C cable is one meter.

<< (I tried swapping to an (obscenely expensive) Apple-branded 3m Thunderbolt 4 cable and this didn't improve things. However FWIW, I believe that hot swapping the cable in the SAME port will restore full resolution.)>>

That should improve things, because that cable is obscenely expensive because it should have almost no attenuation losses, even at 3 meter length, because it is an ACTIVE cable. It re-drives the signals, likely into a fiber-optic that runs the length, then converts them back to electrical at the far end.

I don't know of standard data rates for a 5K by 1440 display, but a standard 5K by 2880 display only works at 30 Hz. over USB-C, which is limited to just under 20 G bits/sec (all outbound)

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Answer 6

Feb 28, 2025 10:27 AM in response to Mike G.

the display also features HDMI 2.0. but that only supports put to 4K at 60 Hz. HDMI ULTRA cables can be longer, but if the display can't run that fast, it is moot.

and it only has one port of each flavor, so a two-cable solution is not likely to work..

DisplayPort is what you are using, either over USB-C cabling or with a cable/adapter to a bona-fide DisplayPort cable-end. Both are usually limited to one meter max, but if your super-expensive ACTIVE thunderbolt cable can also support USB-C that should be a solution.

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Answer 7

Mike G. Author

Level 2

441 points

Feb 28, 2025 10:42 AM in response to Grant Bennet-Alder

The monitor's specs list HDMI 2.1.

Would I be better off using something like this: https://www.amazon.com/dp/B0D1SQSDMN (which conveniently comes in a 10' option)? I'm suspicious due to the comment that despite generally supporting 8k@60hz, it only supports 4k for MacOS...

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Answer 8

Mike G. Author

Level 2

441 points

Feb 28, 2025 10:47 AM in response to Mike G.

Either way, I'm suspicious that it's the cable given that the monitor will regularly WORK with the cable... it's just that Mac OS decides to downgrade the resolution when I restart and I have to swap the port to force MacOS to actually determine the supported resolution and correct it.

... and the fact that unplugging the ethernet cable makes the monitor work also tells me that MacOS is doing something very wrongly-- or at least very poorly documented/communicated...

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Answer 9

Feb 28, 2025 11:56 AM in response to Grant Bennet-Alder

the specs I was seeing were on a third-party spec site.

The specs on the company site suggest that HDMI 2.1 IS supported. if that is true and you can obtain an HDMI 2.1 ULTRA Cable, that would solve the cable-length issue.

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Answer 10

Mike G. Author

Level 2

441 points

Mar 2, 2025 1:45 PM in response to Mike G.

Update: Direct connecting with an HDMI cable does not work. I connected a HDMI2.1 cable directly from the Mac to the monitor, unplugged everything else (except power), and booted. The Mac only recognized a 3840 maximum horizontal resolution. (Because there is only one HDMI port on the monitor, I can't use the trick of swapping ports to force MacOS to re-determine the resolution -- which is what's required to make USB-C connection work.) So Mac Studio will not support 5120x1440 via HDMI.

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Answer 11

Mike G. Author

Level 2

441 points

Mar 4, 2025 9:30 AM in response to Mike G.

Aha, I think I've solved it! After problems with both USB-C and HDMI, I ended up trying a Thunderbolt4->DisplayPort adapter and it seems to have fixed things! My monitor has remained on full-resolution through a couple of reboot cycles, even with all other peripherals plugged in. Yay!!

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Answer 12

Mike G. Author

Level 2

441 points

Feb 28, 2025 2:41 PM in response to Grant Bennet-Alder

Ah thanks! (Sorry, I guess I was not seeing anything >4k in a multi-display configuration … which isn’t what matters in my single-display setup.)

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Mac Studio M2 max struggling to drive 5K / 5120x1440 ultra-wide monitor