M4 Pro Mac mini: 3x 4K display issues, conflicting specs

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Level 1

29 points

M4 Pro Mac mini: 3x 4K display issues, conflicting specs

I've been having issues getting my M4 Pro Mac mini to consistently support 3 external 4K displays. I've spoken with Apple support about the issue, and it honestly made the whole situation even more confusing. I'm writing here to detail my experience and see if anyone else can verify what I've been told.

The mini is connected to x3 4K displays, with the following specs:

x1 4K @ 240hz over DP Alt (type C with DSC)

x1 4K @ 120hz over HDMI 2.0 (with DSC)

x1 4K @ 60hz over DP Alt (type-C)

For years I had run the 4K 240hz and 4K 60hz monitors side by side without issue. Recently, I added the third 4K 120hz monitor into the mix, and that's where the bug started to occur. Upon plugging the monitor in, it simply would not connect to the Mini. Wouldn't show up in Settings or anything, and detecting displays did not help. However, as soon as I disabled Display Stream Compression (DSC) on my 240hz monitor, forcing the refresh rate down to 120hz, the third monitor would connect. What's strange is that I can then re-enable DSC on that 240hz monitor after connecting the third monitor, and all three stay connected.

Before calling up Apple support, naturally I looked up the exact supported display configurations for the M4 Pro Mac mini. As detailed on this page the M4 Pro is officially supported for x3 displays at either 6K 60hz, or 4K 144hz. Given that all I'm trying to do is run two 4K displays at 120hz, and one at 60hz, this configuration is within spec. I am perfectly fine with the 240hz monitor bumping down to 120hz in order to connect the third 4K display. Unfortunately, the mini doesn't do this upon connecting the third display. The machine prioritizes maintaining the 240hz option for the monitor, even if I manually select 120hz from the dropdown, and opts to leave the third display disconnected. Assuming this was a firmware or software bug, I decided to call support, and that's where things got murky.

After an initial conversation trying to explain this debacle to a low level support rep, I was pretty quickly migrated to higher level support to deal with the issue. The higher-level support rep came on the phone with a very confident and quick response claiming that the M4 Pro chip is only capable of running x3 monitors at 6K 60hz. Officially, x3 4K monitors were unsupported in general, and so support could not help me any further.

I was surprised at not only how incorrect the statement was, but also how confidently and swiftly it was delivered before I even had a chance to say hello lol (no hate or anything, the guy was nice, maybe just a little hyperactive). I explained to him that the support page I'd seen listed x3 monitors at 144hz, and he said that was wrong. Eventually, I got him to manually enter the exact URL I was looking at (the same one attached above) and suddenly, he found himself as surprised as I was. The page he was looking at was apparently different, and indeed, it is different on a few other Apple spec pages, linked here and here.

After the surprise wore off, he returned to me with an attempt at an answer. He believes that the model I bought, according to its serial number, is attached specifically to the spec sheet he pulled up. He claimed that Apple silently updates its M4 Pro Mac mini models over time, and that the version I have might be subtly different from the version listed on the most current spec sheet, with different display controllers, different firmware, etc. I was very surprised to hear this, as this information cannot be verified or backed up anywhere online.

So I asked him: what are the chances that the spec sheet he was looking at had an error, leaving out the line about x3 144hz 4K display support? He quickly shot down the idea, noting that he used to actually work in the very department that created those spec sheets, and that for legal reasons, the department has to be extremely thorough.

I figured that made sense, but after thanking him and hanging up, I thought a bit more on it...

It appears I've hit a word limit. Sorry if it's long, but I believe the details are significant and quite relevant to this issue. For that reason, I'm linking to a reddit post I've made concluding the rest of my post. Thanks for your time!

[Edited by Moderator]

Mac mini, macOS 26.5

Posted on Jul 19, 2026 5:44 PM

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Answer 1

cellidonuts Author

Level 1

29 points

Jul 20, 2026 9:03 AM in response to cellidonuts

Gotta credit my girlfriend on this one because it was a great idea. She advised that I check the internet archive's wayback machine on the aforementioned links. By doing so, I can cross-check Apple's M4 Pro documentation over time, and analyze how the various different spec pages line up. If what the high-level support rep said is true, and Apple's spec sheets team is as thorough and precise as he claims they are, then back when I bought my Mac mini, the support pages would have unanimously left out the line about triple 4K 144hz support. Only recently-updated pages should show that line, indicating that the support rep is correct, and that Apple discreetly changes the firmware and capabilities of the M4 Pro, updating spec sheets, all while not announcing this publicly.

Well, it turns out that I was right to be skeptical that Apple would do such a thing. When analyzing the various support pages in the wayback machine, you can clearly see that they have always had conflicting information. As soon as December of 2024, before I'd even bought my model, one spec sheet claimed triple 144hz 4K support, while another didn't mention it at all. The takeaway: there has ALWAYS been inconsistency across the spec sheets.

as recommended I’ll be calling support again and will take care to mention this. Thank you to everyone for your help!

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Answer 2

Jul 19, 2026 6:22 PM in response to cellidonuts

exactly what displays are you connecting? or a link to their specs?

exactly what cables, adapters and Docks are you using to make the connection? please mention every item in the chain.

NB> the specs claiming 144 Hz specifically name Thunderbolt or HDMI connections. DisplayPort derived from USB-C has FAR less bandwidth, and will support far lower refresh rates and resolutions.

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Answer 3

MrHoffman

Level 10

159,069 points

Jul 19, 2026 7:29 PM in response to cellidonuts

Tech specs:

I read that as one 4K display at 240 Hz permissible via Thunderbolt or HDMI, and the others at 60 Hz and specified resolutions.

As for deconflicting the Mac mini tech specs with the cited Mac mini display support support article, that’s on Apple to resolve. Call’m back.

NB: Studio with M4 Ultra can get into the configuration you’re trying, with 4 displays at 4K at 240 Hz:

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Answer 4

MrHoffman

Level 10

159,069 points

Jul 19, 2026 8:11 PM in response to cellidonuts

cellidonuts wrote:

Hi, yes I’m aware 240hz isn’t supported. The issue isn’t that it won’t do 240hz. The issue is that the Mac mini doesn’t intelligently step down from 240 to 144 or 120 when the third monitor is connected. Instead, it opts to preserve the 240hz connection by omitting the third monitor entirely.

And from the tech specs, two is the limit.

Apple needs to sort the conflict in those two docs. Re-contact Apple, and continue the discussion.

Let us know the resolution; which of the two is correct, or if neither is correct.

As for displays, AFAIK Apple only uses the supported-resolution settings reported by the monitors — whichever monitor vendor(s) and model(s) and whatever thr hardware display configuration might be. The third-party SwitchResX app can report this monitor-reported data, though I have no experience with that app.

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Answer 5

Jul 20, 2026 9:10 AM in response to cellidonuts

[In my opinion] the specs are not wrong, they are simply more nuanced than you are reading.

NB> the specs claiming 144 Hz specifically name Thunderbolt or HDMI connections. DisplayPort derived from USB-C has FAR less bandwidth, and will support far lower refresh rates and resolutions.

NONE of your displays support direct ThunderBolt connections, and you have yet to respond about how you are interfacing/cabling the ASUS display.

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Answer 6

Jul 19, 2026 6:39 PM in response to cellidonuts

Re: reddit post.

If you have more to say, simply click (Reply) to your original posting and add the additional information.

Anything that is part of a discussion becomes a permanent reference for readers to find by searching, and if an important part disappears because it is removed from another site, then the discussion will be incomplete and FAR less helpful.

All original materials must be posted here on the forums, not on any third-party site.

You can certainly link to authoritative sites with import technical information, but links to other discussion sites with opinions of "just some guy" are subject to removal.

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Answer 7

Jul 19, 2026 7:50 PM in response to cellidonuts

cellidonuts wrote:

I just tried to, but it was taken down, not really sure why. The Reddit link was removed and there wasn’t anything unsavory.

You just need to stick with support here where there is no self promotion to other sources for upvotes and where Apple has no way to moderate that site if one of the replies at a later date were to include content that would not be acceptable in a link provided here. You can certainly include more information here in another reply or use the Additional Text option (Page Icon) when posting to add information beyond the character limit of a single post.

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Answer 8

cellidonuts Author

Level 1

29 points

Jul 19, 2026 7:57 PM in response to MrHoffman

Hi, yes I’m aware 240hz isn’t supported. The issue isn’t that it won’t do 240hz. The issue is that the Mac mini doesn’t intelligently step down from 240 to 144 or 120 when the third monitor is connected. Instead, it opts to preserve the 240hz connection by omitting the third monitor entirely.

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Answer 9

cellidonuts Author

Level 1

29 points

Jul 19, 2026 7:40 PM in response to Grant Bennet-Alder

I just tried to, but it was taken down, not really sure why. The Reddit link was removed and there wasn’t anything unsavory.

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Answer 10

Jul 20, 2026 9:34 AM in response to Community User

MrHoffman wrote:

<< Based on the Mac mini with M4 Pro tech specs, looks like one monitor past 60 Hz is supported. >>

To the best of my knowledge, there is no bandwidth sharing between display generators.

• HDMI ports in M2 and later Macs can run slightly faster than the Thunderbolt-3 or -4 speeds or 40 G bits/sec to support HDMI 2.1 at 42.0 G bits/sec, supporting uncompressed 10 bits/color 4K at 144 Hz.

• ThunderBolt -3 or -4 ports, when connected to a Thunderbolt Display, can support UHBR10, at 38.69 G bits/sec, also supporting DisplayPort 4K displays uncompressed at 10 bits/color at up to 144 Hz.

• USB-C derived displays using DisplayPort, either derived with common dongle adapters or DisplayPort Alt Mode, can only run the highest standard speed that can be supported by the protocol (when starting with maximum 20 G bits/sec USB-C) is 17.28 G Bits/sec HBR2. That allows a 10 bits/color 4K HDR display to run directly at up to 60 Hz, NOT Faster.

--------

There is one more wonky case, first implemented by the Apple Pro Display XDR over a Thunderbolt-3 or -4 connection.

The 6K Apple Pro Display XDR, which macOS allows to connect using two HBR3 connections [nominally 25.92 G bits/sec] to a Mac, doesn't support Display Stream Compression (DSC). That would be 51.84 Gbit/s, impossible for Thunderbolt 3, but it works because the two 3008×3384 10bpc 60 Hz 648.91 MHz signals of the XDR display only require 38.9 Gbit/s total and Thunderbolt does not transmit the DisplayPort stuffing symbols used to fill the HBR3 bandwidth.

https://en.wikipedia.org/wiki/Thunderbolt_(interface)

This allows a Mac with an EXTRA display generator to use it to make some otherwise-impossible connections over Thunderbolt, committing TWO display-generators and dividing the display into Right and Left halves and re-assembling them in the display.

This feature is not supported over USB-C or with any USB-C based dongle adapters.

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Answer 11

Jul 21, 2026 12:47 PM in response to cellidonuts

Your ASUS display has HDMI and DisplayPort inputs.

your Mac has HDMI, USB-C, and Thunderbolt outputs.

¿Exactly what cables, adapters, and Docks are you using to make the connection, to the ASUS display?

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