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

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

#21

Post by kalleboo »

tom_ wrote: post #14
bsimpson wrote: post #4

Wouldn't HiDPI be 1080p@2x? Is that still available?

Yeah. I don't get it. If you've got a 3840x2160 display, intended use on macOS as a 1920x1080@2x display, what is the advantage of using a 7680x4320 buffer? Everything is drawn at twice the width and height - and then gets scaled down to half the width and height. Is there actually a good reason to do this? (I use my M4 Mac with 4K displays, and 5120x2880 (2560x1440@2x) buffers. That sort of thing does work, though i…

> what is the advantage of using a 7680x4320 buffer? Everything is drawn at twice the width and height - and then gets scaled down to half the width and height. Is there actually a good reason to do this?

Text rendering looks noticeably better rendered at 2x and scaled down. Apple's 1x font antialiasing is not ideal.

Especially in Catalyst/SwiftUI apps that often don't bother to align drawing to round points, Apple's HiDPI downscaling has some magic in it that their regular text rendering doesn't.

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

#22

Post by arjie »

I'm sure you've already given this a crack via some other technique (I just Cmd-F for it and didn't find) but I have had monitors with confusing EDIDs before that MacOS didn't handle well and the "screenresolution" CLI app https://github.com/jhford/screenresolution always let me set an arbitrary one. It was the only way to get some monitors to display at 100 Hz for me and worked very well for that since the resolution is mostly sticky.

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

#23

Post by TheTon »

tom_ wrote: post #14
bsimpson wrote: post #4

Wouldn't HiDPI be 1080p@2x? Is that still available?

Yeah. I don't get it. If you've got a 3840x2160 display, intended use on macOS as a 1920x1080@2x display, what is the advantage of using a 7680x4320 buffer? Everything is drawn at twice the width and height - and then gets scaled down to half the width and height. Is there actually a good reason to do this? (I use my M4 Mac with 4K displays, and 5120x2880 (2560x1440@2x) buffers. That sort of thing does work, though i…

Yes 1920x1080@2x absolutely works on M4. I use this mode all day every day.

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

#24

Post by LuxBennu »

Sadly I have the issue on a new m5 air. I have a 60hz 4k work monitor and two high refresh 4k gaming displays. The 60hz pairs fine with either gaming monitor, but the two gaming ones together and one just doesn't get recognized. Spent way too long trying new cables before realizing it's a bandwidth limitation.

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

#25

Post by cosmic_cheese »

MBCook wrote: post #17
whatever1 wrote: post #13

How did none of the Apple devs notice this? 4k 32" inch is the industry standard for HiDPI monitors.

Apple doesn’t make an 4k external monitor. They’re likely all on Studio Displays.

And prior to Apple’s re-entry into the display market, everybody internally was likely on 2x HiDPI LG UltraFine displays or integrated displays on iMacs and MacBooks.

Fractional scaling (and lately, even 1x scaling “normal”) displays really are not much of a consideration for them, even if they’re popular. 2x+ integer scaling HiDPI is the main target.

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

#28

Post by FireBeyond »

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...

No, it didn’t get fully fixed.

Fucking with DP 1.4 was how they managed to drive the ProDisplay XDR.

If your monitor could downgrade to DP 1.2 you got better refresh rates than 1.4 (mine could do 95Hz SDR, 60Hz HDR, but if my monitor said it could only do 1.2, that went to 120/95 on Big Sur and above, when they could do 144Hz HDR with Catalina).

I would be absolutely unsurprised if their fix was to lie to the monitor in negotiation if it was non-Apple and say that the GPU only supported 1.2, and further, I would be also unsurprised to learn that this is related to the current issue.

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

#29

Post by sgerenser »

wmf wrote: post #5

This is not a normal retina configuration. This is a highly unusual configuration where the framebuffer is much larger than the screen resolution and gets scaled down. Obviously it sucks if it used to work and now it doesn't but almost no one wants this which probably explains why Apple doesn't care.

I don’t know why this was downvoted, I agree that this is a highly unusual configuration. Why render to a frame buffer with 2x the pixels in each direction va the actual display, only to then just scale the whole thing down by 2x in each direction?

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

#30

Post by Gigachad »

whatever1 wrote: post #13

How did none of the Apple devs notice this? 4k 32" inch is the industry standard for HiDPI monitors.

Tbh I'm not even sure what the issue is here. I have a personal M1 macbook and a work M4 and a 4k display. I don't see any issues or differences between them on my display. The M4 seems to be outputting a 4k image just fine.

The article could just be AI slop since it just contains hyper in depth debugging without articulating what the problem is.

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