Macbook Pro M3 Pro refresh rate stuck at 60hz after working at 144hz

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Macbook Pro M3 Pro refresh rate stuck at 60hz after working at 144hz

I just got my M3 Pro Macbook Pro and for a week it has been great. I purchased USB C to HDMI cables for my two X27q monitors (1440p/165hz). I'm using a Caldigit Element hub. It's thunderbolt 4. For a week both monitors were running at native res 1440p at 144hz perfectly. This morning one monitor is allowing 60hz or 75hz while the other was 144hz, then 120 hz, then once more allows 144 hz. Last night I put my mac to sleep and this morning it just stopped working correctly. Tested monitors with a pc I have and they both run 165hz. I have reason to believe it is software related. Updated to Sonoma 14.4.1. Any help?

Cables I'm using: https://www.amazon.com/uni-Thunderbolt-Compatible-MacBook-Surface/dp/B075V5JK36?th=1

Monitors I'm using: https://www.amazon.com/HP-27-inch-Adjustment-FreeSync-Technology/dp/B0949KL83T?th=1

Dock I'm using: https://www.amazon.com/CalDigit-Thunderbolt-Element-Hub-Multi-Port/dp/B08FQX8MXQ

TLDR: 2 identical monitors using 2 identical cables connected to a capable thunderbolt 4 dock is no longer displaying 1440p @ 144hz even though it has since I got the machine.

Posted on Mar 30, 2024 8:37 AM

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Answer 1

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andrij11 Author

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18 points

Apr 8, 2024 7:31 PM in response to andrij11

Problem was the USB C to HDMI cable. While the cables did work, waking from sleep after several hours caused issues. Switched to USB C to Displayport and no issues for a week now, including running at high refresh rates.

Solution: Only use Displayport. Avoid HDMI.

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Answer 2

Mar 30, 2024 9:03 AM in response to andrij11

The data rates require to run a full color high-end display at full resolution require a lot of accommodation in all that Hardware. Squashing so much data onto ONE ThunderBolt cable may be difficult. if errors or dat dropouts occur, the resolution and/or refresh rate WILL be reduced in modern MacOS.

One display at 2560 by 1440 at 144 Hz requires USB-2 at 14.4 G bits/sec. two requires twice that. The way ThunderBolt cables attain nominal 40 G bits/sec (actual sustained data rates closer to 32 G bits/sec) is to "turn around" the inbound conductors into outbound conductors when needed. Two displays running at different timing may be difficult to run reliably that way.

I recommend you move at least one of these displays to a cable that does NOT go through the same Thunderbolt cable to the same Dock.

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Answer 3

andrij11 Author

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18 points

Mar 30, 2024 11:24 AM in response to Grant Bennet-Alder

Each monitor has it's own cable into the dock, so that's 2 TB4 connections. I have one Logitech Bolt adapter connected in the USB-A port for my MX Master 3S mouse & MX Mini keyboard. That's it, nothing else is connected. Nothing is also connected to the Macbook except that dock cable to the right side TB4 port (near the HDMI).

Some Reddit post suggests USB C to HDMI cables aren't the greatest choice for this application. Not sure if you can validate this claim, however they state Using USB-C to DP cables avoids the conversion from DP to HDMI & that it's DP that gets carried between your Apple Macbook Pro and the Caldigit Element Hub. Effectively using USB C to DP is one less hoop to jump through so the whole apparatus is more reliable and efficient?

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Answer 4

andrij11 Author

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Mar 30, 2024 10:49 AM in response to Grant Bennet-Alder

Thanks for your response Grant!

Looking over Apple's claims, my setup should support Two displays up to 6K at 60Hz over Thunderbolt. My assumption that two QHD monitors at 144Hz was less demanding was incorrect. I guess while QHD is less demanding that 6K, the combined refresh rate of both makes up for it?

I went ahead and power cycled the dock but that didn't fix anything. I decided to disconnect the monitors from the dock and when I reconnected both were operating correctly! So that's good. 😊

However I spent a good amount of time cable managing and hiding the powerstrip, cables, dock, etc. under my desk in a cage. I would hate to have to repeat this fix often and have to crawl under my desk every few days. What can be done to fix this? I assumed CalDigit was highly regarded so I would avoid compatibility and reliability issues with going with them. I know this is an Apple forum & not CalDigit's but any advice or remedies would help.

Thanks again Grant! 👋🏻

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Answer 5

Apr 9, 2024 6:54 AM in response to andrij11

<<. Some ... suggests USB C to HDMI cables aren't the greatest choice for this application. >>

I wholeheartedly agree.

Some of the newest higher-end Macs 2023 and later support HDMI 2.1 directly, BUT: NO adapters to HDMI 2.1!

You either connect a straight "ULTRA" HDMI cable directly, or all bets are off.

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Answer 6

Mar 30, 2024 12:42 PM in response to andrij11

<<. USB from dock to HDMI or DisplayPort adapter electronics is currently over one meter because the dock ports are TB4 and the cables I am using are TB4. Intel states up to 2 meters (6.56 feet) in length. >>

A ThunderBolt cable has double the conductors, but that does NOT double the allowable distances when used to connect the very highest speed displays (which yours individually, are not). Also most HDMI adapters or DisplayPort adapters are USB devices, NOT ThunderBolt devices.

I stand by what I wrote above:

For very highest speeds, USB from Dock to HDMI or DisplayPort adapter electronics is limited to ONE meter.

All of this part of the discussion is irrelevant to what you came in with. Individually, each of your displays is working just fine. It is only the overwhelmingly high data rate of the combination of all these devices on one Thunderbolt cable that is giving you difficulty.

If you were willing to drop one or the other or both of the refresh rates to 75Hz, it would all fit fine.

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Answer 7

Mar 30, 2024 11:00 AM in response to andrij11

That Thunderbolt cable does not have Extra bandwidth when two displays are connected at up to 144 Hz. If you have a drive on that dock as well, you have simply over-configured what can be on ONE Thunderbolt cable without slowdowns.

What else is connected to that dock?

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Answer 8

Mar 30, 2024 3:01 PM in response to andrij11

The Mac asks the display all the time whether there were any transmit errors. Up until yours stopped working at its top settings, the great wads fo data had managed not to collide, no errors were generated and you 'got by'.

Then they collided, generated transmission errors, the display reported those errors to the Mac, and the Mac lowered the data rates.

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Answer 9

Mar 30, 2024 11:54 AM in response to andrij11

the pinch point is in the ThunderBolt port from Mac to dock.

The ones to each device are fine. No need to fiddle with those. Individually, they are working as expected.

For highest speeds, USB from dock to HDMI or DisplayPort adapter electronics is limited to ONE meter.

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Answer 10

andrij11 Author

Level 1

18 points

Mar 30, 2024 12:28 PM in response to Grant Bennet-Alder

USB from dock to HDMI or DisplayPort adapter electronics is currently over one meter because the dock ports are TB4 and the cables I am using are TB4. Intel states up to 2 meters (6.56 feet) in length. The TB4 cable from the dock to the Mac is under one meter (0.8 m exactly) so I should get highest speeds with this current setup if I understand correctly.

Also I'm using my Mac in clamshell mode, so the inner display isn't being added to the mix. Forgot to mention that.

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Answer 11

andrij11 Author

Level 1

18 points

Mar 30, 2024 1:39 PM in response to Grant Bennet-Alder

Alright well thanks for explaining this all to me Grant.

I dropped both displays down to 120 hz to match the Promotion display. Let's see if this might be enough wiggle room for it to not to act up again.

What seems unanswered to me is how this setup was not overwhelming all week until this morning after the Mac awoke from sleep mode after 8 hours of doing nothing. Only applications open were Notion and Spark (notes and email apps). Also why unplugging and replugging the monitors from the dock fix this data rate limit?

Thanks again Grant 🤓

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Macbook Pro M3 Pro refresh rate stuck at 60hz after working at 144hz

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