M4 Mac Mini @ Sequoia - HiDPI Resolution missing

[hellerchr]

Hi @waydabber,

I have the LG 38GN950 (3840x1600) screen. I usually use this with the resolution 3200x1333 @ HiDPI mode with my macbook pro (M2 Pro @ Sonoma).

Since today I also have a mac mini (m4 base model) and I am unable to get this resolution working on it :-(.

The highest HiDPI it offers me is 2560x1067, which scales the UI elements too large for me.

Does anyone have any idea how I could get 3200x1333 to work in HiDPI mode on this setup?

PS: I use the display via HDMI and at 75hz. The only alternative refresh rate that is offered is 30hz. I was able to use the 3200x1333@75hz HiDPI with the same cable on the m2 pro macbook pro.

PPS: I have order a DP1.4 8k 60hz, 4k 240hz usb-c to displayport cable, which should arrive tomorrow to try if that makes any difference.

Thanks a lot,
Chris

[waydabber]

You need to enable flexible scaling.

https://github.com/waydabber/BetterDisplay/wiki/Fully-scalable-HiDPI-desktop

Just testing the entry level m4 mini, had no trouble going up to 3840x2160p HiDPI with it and all the interim resolutions. Everything should work fine. I am super impressed with the m4 mini (I am testing the entry level one), it is such a great value for money. The app seems to have zero issues with it so far luckily. :)

[waydabber]

But just did some more tests with various displays. Interestingly when connecting via USB-C, there is still a 3072px HiDPI horizontal limit in the resolution list (even though the reported limit is 3840px and over HDMI it works). Strange. Maybe this is why you can't get higher resolutions.

UPDATE: others reported different (higher) limits over USB-C so there might be some other factors.

[hellerchr]

@waydabber
I just did a factory reset of my Mac and cleanly installed the latest better display and only touched it to enable the flex mode. I connect via hdmi cable (usb-c will arrive tomorrow). This is how it looks like for hidpi I am limited to 2560x, I think I could live with the 3072px that you mentioned, but the 2560 is just too large/unusable to me. Any idea what's going on here? Do you need more detailed information?

[hellerchr]

PS: when I switch to the other Hz rates the resolution options stay the same

[waydabber]

Not exactly sure what goes on to be honest and why is the limitation. Now as I am testing it, it indeed behaves rather strangely for me as well - the available resolutions seem to depend on what displays I connect and in what order. Maybe things will be more stable in 15.2.

[hellerchr]

Update: The usb-c thunderbolt to displayport cable has resolved this issue. I can now use the 3008x1254 resolution (80%) width HiDPI. Absolutely happy now :-)

[hellerchr]

PS: the former used HDMI was just 2.0, even though it worked with older mac versions it was an issue with sequoia

[waydabber]

Generally it seems like since the M4 mini has a somewhat awkward external display support (1x8K+1x5K or 2x6K+1x5K for the M4 mini and 1x8K+1x6K or 3x6K for the M4 pro mini) the system must prioritize a limited-sized framebuffer unless a 8K framebuffer is not absolutely necessary (that is, when a 8K display or a 5K+ ultrawide is connected). Otherwise if the system would simply grants 8K to the first display connected (although it does not seem to be absolutely necessary, like for a 4K display), one less display could be connected later on. Similar limitations existed (but not in such a pronounced manner) for some other Apple Silicon Macs as well.

[romancin]

Dell U4021qw monitor here, 40 inches 5K2K resolution, M4 base Mac mini. Tested it over Thunderbolt and DisplayPort 8K adapter over USB-C, and it seems the limit of 6K is still there :(

@waydabber Is there something we can do or using virtual displays is the only option?

Thank you very much for your testing and help!

[waydabber]

Strange. Some reported success with a 5Kx2K display on the M4 here: https://forums.macrumors.com/threads/5k2k-at-120hz-with-mac-mini-m4.2441289/unread.

I tried to explain in the forums why I think the limitation kicks off (if the OS grants a 8K framebuffer for a display, one less further display can be connected as the entry level Mini supports 2 displays if one is 8K, otherwise it supports 3 displays). But technically the M4 mini should be able to handle a 8K framebuffer (so 3840px HiDPI) which means there is some hope that Apple will tweak this.

[romancin]

Is there anyway to force 8K framebuffer using BetterDisplay to test of it works with this monitor?

In the meantime, are there any technical differences between using flexible scaling and virtual displays I should take into account?

Thank you @waydabber !

[waydabber]

Mirrored virtual screens work fine for most of the time, but some users report sleep issues or mouse cursor issues depending on setup. There should not be performance issues. Also, virtual screens are limited to 60Hz (although you can add custom 120Hz, I don't think it works, despite some users reporting so).

Some ultrawide users at MacRumors forum that 5k2k enables 8K HiDPI (much like 8K displays - which I can test). Is this not the case?

[romancin]

No, it is not my case. Reading the MacRumors thread you mentioned, they are speaking about U4025qw, which is 120Hz monitor. More bandwidth is needed for it? Mine is u4021qw, which is 60Hz only.

[romancin]

It looks like I am not alone (https://forums.macrumors.com/threads/5k2k-at-120hz-with-mac-mini-m4.2441289/post-33564197) even M4 Max can’t achieve 4K HiDPI with this monitor, which works perfect with my MBP M3 Max…

Something weird happens with these M4 processors…

[effJkeee]

@waydabber do you have a chance to test on a basic M4, connect two 4K monitors, each has a framebuffer for hidpi will be 3840px or is that not true?

[waydabber]

I did not try that. Did someone report that this is what happens?

[terabyte128]

I'm having what seems to be a related issue with my new M4 Pro MacBook Pro.

I have an 40WP95C-W (LG 5k2k) monitor. On my M1 Pro MBP, it works fine at a HiDPI resolution of 3840x1620. (Natively, BetterDisplay not required.) But when I connect my new computer, the highest I can go without getting all the way up to the native resolution is 3360x1418:

Enabling flexible scaling in BetterDisplay doesn't seem to help; it still shows as the max scaled resolution:

Connecting to the display over HDMI is worse, though that might just be my cables. I did also try adjusting the refresh rate down from the native 72 Hz to 60 Hz, but that didn't help either.

[waydabber]

It's interesting how some seem to be able to achive 3840px on a 5K2K display (https://forums.macrumors.com/threads/5k2k-at-120hz-with-mac-mini-m4.2441289/unread), some 3360px and while others only 3072px.