Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

smcleod.net

Post reply on HN
Print view View original

101–110 of 180 posts

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#101

Post by smcleod »

extr wrote: post #87
compounding_it wrote: post #35

The ideal work/coding resolutions and sizes for macOS that I would suggest if you are going down this rabbit hole. 24 inch 1080p 24 inch 4k (2x scaling) 27 inch 1440p 27 inch 5k (2x scaling) 32 inch 6k (2x scaling) Other sizes are going to either look bizarre or you’ll have to deal with fractional scaling. Given that 4k is common in 27/32 inches and those are cheap displays these kinds of problems are expected. I hav…

If you actually care about this stuff you are going to run something like https://github.com/waydabber/BetterDisplay which easily allows for HiDPI @ 4K resolution, it does not "look bizarre" or "require fractional scaling". This is what the OP is about. I do the same thing, I run native res w/ HiDPI on a 27" 4K screen as my only monitor, works great.

Unfortunately BetterDisplay cannot set HiDPI @ 4K on the M5 machines - that was the first thing I tried.

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#102

Post by smcleod »

Aurornis wrote: post #65
comex wrote: post #10

Well, it sounds like a real issue, but the diagnosis is AI slop. You can see, for example, how it takes the paragraph quoted from waydabber (attributing the issue to dynamic resource allocation) and expands it into a whole section without really understanding it. The section is in fact self-contradictory: it first claims that the DCP firmware implements framebuffer allocation, then almost immediately goes on to say i…

Agree. I started reading the article until I realized it wasn’t even self-coherent. Then I got to the classic two-column table setup and realized I was just reading straight LLM output. There might be a problem but it’s hard to know what to trust with these LLM generated reports. I might be jaded from reading one too many Claude-generated GitHub issues that look exactly like this that turned out to be something else.

Parts of it were pasted from my Claude Code Logs, Parts were written by me - and the table - that was me!

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#103

Post by smcleod »

pier25 wrote: post #69
smcleod wrote: post #59

Earlier quoted context omitted.

It's in the environment and test setup (26.4 at the moment, but it is the same across all 26.x releases I've tried).

I'm still on Sequoia and haven't noticed these issues on my M4 Pro.

Out of interest - whats the output of `system_profiler SPDisplaysDataType`?

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#105

Post by Someone »

> This aligns with our findings. The M4/M5 DCP firmware implements a conservative framebuffer pre-allocation strategy that:

> Caps the HiDPI backing store to approximately 1.75x the native resolution (6720x3780 for 3840x2160 native), rather than the 2.0x needed for full HiDPI (7680x4320)

So, that could be an off by one bug? That might be testable by tweaking the system to think the display supports an even higher resolution.

Also, instead of messing with the Display Override Plist, patching drivers, etc, did they try using the “Advanced…” button in the “Displays” UI? They don’t mention they did.

For me (with a 27 inch 4K monitor not on M4 or M5) that replaces the 5-way choice by one with a list of 11 choices. With the then appearing “Show all resolutions” toggle, that becomes 18.

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#107

Post by nuker »

smcleod wrote: post #64
nuker wrote: post #7

Send it to Tim Cook email. It worked for me fixing DisplayPort DSC bug. After Catalina, later MacOSes lost ability to drive monitors at higher than 60Hz refresh. Apple support tortured me with all kinds of diagnostics, with WontFix few weeks later. Wrote email and it got fixed in Sonoma :) https://egpu.io/forums/mac-setup/4k144hz-no-longer-available...

I don't expect emails to get through to busy CEOs of huge companies like Apple unless you're really lucky and they make it through some automation, but I have dropped him an email just in case. I guess you never know.

Helps if there are support case numbers with attempted diags, maybe.

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#108

Post by arvinsim »

nuker wrote: post #7

Send it to Tim Cook email. It worked for me fixing DisplayPort DSC bug. After Catalina, later MacOSes lost ability to drive monitors at higher than 60Hz refresh. Apple support tortured me with all kinds of diagnostics, with WontFix few weeks later. Wrote email and it got fixed in Sonoma :) https://egpu.io/forums/mac-setup/4k144hz-no-longer-available...

Didn't know that. This probably explained why MacOS felt sluggish compared to my Windows PC even though I was using them on the same 144hz monitor.

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#109

Post by smcleod »

Someone wrote: post #105

> This aligns with our findings. The M4/M5 DCP firmware implements a conservative framebuffer pre-allocation strategy that: > Caps the HiDPI backing store to approximately 1.75x the native resolution (6720x3780 for 3840x2160 native), rather than the 2.0x needed for full HiDPI (7680x4320) So, that could be an off by one bug? That might be testable by tweaking the system to think the display supports an even higher res…

I tried quite a few things in the "Advanced" section of BetterDisplay - is there something specifically you're suggesting?

Re: New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays

#110

Post by paozac »

skullone wrote: post #3

I thought I was going crazy when my new m4 seemed "fuzzier" on my external 4ks. I tried replicating settings from my old MacBook to no avail. I wonder if Apple is doing this on purpose except for their own displays.

Same here, I tried all combinations with BetterDisplay but kept getting fuzzy fonts. It was very frustrating on a large 5k2k display
Post reply on HN