Why do ARM Mac’s suck with external monitors?

[Zest28]

I was shopping for new external monitors, and I managed to get an amazing discount / deal on a brand new Dell Ultrasharp display, only to be warned not to use it with Mac’s as it has terrible scaling issues.

I have the same problems with my current Samsung 4K display as the letters are small as hell, and I basically have to change the resolution in Mac OS.

So why are ARM Mac’s terrible with external monitors?

 

[leman]

They work just fine with external monitors as long as they have common aspect ratio, high-dpi and modern connectivity.

 

[jwahaus]

What are these "terrible scaling issues" you speak of? I've used a variety of monitors with zero issues.

 

[iStorm]

It has nothing to do with Arm Macs. It's more to do with how macOS handles scaling. Someone can probably explain it better than I can, but there are other threads on this topic. Like others have said, it's fine as long as you have a high-dpi display. You want to look for an appropriate resolution based on the size of the display. For example, for a 22" display, you might want 4k; for a 27" display, you might want 5k; for a 32" display, you might want 6k.

I have the same problems with my current Samsung 4K display as the letters are small as hell, and I basically have to change the resolution in Mac OS.

I'm confused with this statement. Wouldn't the letters be "small as hell" on a Windows PC using 100% scaling too? You'd have to change your scaling to something like 200%, which essentially cuts your resolution in half. (It's still outputting 4k, but looks like 1080p.)

 

[pshufd]

I have an M1 Mac mini running 3 Dell Ultrasharp 4k monitors. One is running off USB-C to a Dell U2720Q. One is running off the HDMI port to a U2718Q and one is running off a DisplayLink device to another U2718Q. The monitors are basically the same. It's the display ports that are different. The USB-C monitor can display 3,008 x 1,692 really well. The HDMI display can display 3,008 x 1,692 but the fonts are fuzzy. The scaling shows that this is a "low resolution" display scale. It can display 4k native resolution just fine. The highest resolution that I can use is QHD - macOS allows me to choose QHD or QHD (low resolution).

The 4k monitor off a DisplayLink adapter can display native 4k and HD clearly. Everything between HD and 4k is (low resolution). So basically three of the same monitors but three different levels of resolution support. At this point, I think that it's the display port types rather than the monitors. The USB-C port will go up to 6k and I suspect that the screen or windows gets rendered at 6k and downscaled to 3,008 x 1,692. So maybe you need to use 6k ports to get all of the nice scaled resolutions possible with 4k monitors. I do mean to test that out with my M1 Pro MacBook Pro which has two 6k display outputs.

Next to three monitors is my 2014 iMac 27 - this thing just freaking rocks the display. This iMac (i7, 32 GB RAM, 500 GB SSD) cost me less than a Dell Ultrasharp 27 inch 4k monitor.

So there is funny stuff with monitors but I'm not completely sure of the cause - I do know that the problem isn't the monitors.

 

[vanc]

I also have a Dell 2720Q. It's a overkill for me as I'm a mostly a software developer, not a designer.

My 16' MBP with M1 Pro works fine with it over HDMI. I'm actually using a Dell Thunderbolt 3 Dock and it connects to the monitor via HDMI.

From system report:

 

[pshufd]

I also have a Dell 2720Q. It's a overkill for me as I'm a mostly a software developer, not a designer.

My 16' MBP with M1 Pro works fine with it over HDMI. I'm actually using a Dell Thunderbolt 3 Dock and it connects to the monitor via HDMI.

From system report:

View attachment 2054118

I think that it's the resolution that can be output from the ports rather than strictly the type. On the M1 Pro, it can output 6k. On the M1 mini, it can only output 4k.

At any rate I also have an M1 Pro MacBook Pro and I do mean to test out the scaled resolutions off of it. I guess that I would have been better off with a Mac Studio as that can do 4 x 6k.

 

[Xiao_Xi]

This blog post may help.

Mac external displays for designers and developers, part 2

Since writing about Mac external displays in 2016, not much has changed. LG, Dell, Samsung, and other display makers have either never catered for the specs many Mac designers and developers want, or they’ve reluctantly produced products that have been short-lived or compromised.

bjango.com

 

[kasakka]

MacOS handling for external displays is terrible in general, even on Intel Macs.

• Any display with above 60 Hz refresh rate is unlikely to work right or at a less than max refresh rate, especially if DSC is involved. DSC seems mostly broken on MacOS for anything but Apple's own displays.
• HDMI 2.1 cannot be used even with USB-C to HDMI 2.1 adapters that work just fine on PC/Windows. MacOS limits these to HDMI 2.0 speeds.
• There are no controls for bit-depth or chroma subsampling so if MacOS picks a wrong option you have to do things like DisplayEDID overrides which apparently don't work on Apple silicon and are way outside what an avarage user should learn. For example my LG OLED TV defaulted to 10-bit 4:2:0 which is the worst option for desktop use.
• Scaling levels available vary between models which is totally non-obvious. M1 Pro/Max/Ultra seem to offer more options than regular M1/M2.
• Whether scaling works or not in the first place is arbitrarily decided by Apple. It seems to be based on something naive like "horizontal res is above 4K" because e.g LG DualUp 16:18 2560x2880 does not work with scaling without using BetterDisplay despite having the equivalent PPI of a 32" 4K 16:9 display.
• HDR support working is erratic. You might need to have a very specific refresh rate selected or it just refuses to work on even something standard like a 4K TV. For example the afore-mentioned LG OLED TV never gave me the option while it works just fine on Windows.

Finally the way MacOS handles scaling is clearly not optimal. Windows ends up looking sharper for e.g 4K displays than MacOS does with its more naive scaling that is just "upscale target res 2x -> downscale to native res". For 4K screens at 27-32" usually the appropriate scaling is around 2540x1440 or slightly higher rather than the integer scalable 1080p. These options result in non-integer scaling which does blur the image a little bit.

On Apple's 5/6K screens the issue is just less noticeable because of the higher res of those displays. But if you use anything except the 1:1 scaling option (2560x1440 on the 5K ASD) you will run into the same problems and personally I liked the 5K display with a setting one notch above the "looks like 2560x1440" for the extra desktop space.

To me it seems like Apple should do something to improve on this, even something as simple as a slight sharpening filter might fix the problem. Or maybe they need to get on the AI-upscaling bandwagon considering how much they tout their chips' machine learning capabilities.

 

[kasakka]

I have an M1 Mac mini running 3 Dell Ultrasharp 4k monitors. One is running off USB-C to a Dell U2720Q. One is running off the HDMI port to a U2718Q and one is running off a DisplayLink device to another U2718Q. The monitors are basically the same. It's the display ports that are different. The USB-C monitor can display 3,008 x 1,692 really well. The HDMI display can display 3,008 x 1,692 but the fonts are fuzzy. The scaling shows that this is a "low resolution" display scale. It can display 4k native resolution just fine. The highest resolution that I can use is QHD - macOS allows me to choose QHD or QHD (low resolution).

The 4k monitor off a DisplayLink adapter can display native 4k and HD clearly. Everything between HD and 4k is (low resolution). So basically three of the same monitors but three different levels of resolution support. At this point, I think that it's the display port types rather than the monitors. The USB-C port will go up to 6k and I suspect that the screen or windows gets rendered at 6k and downscaled to 3,008 x 1,692. So maybe you need to use 6k ports to get all of the nice scaled resolutions possible with 4k monitors. I do mean to test that out with my M1 Pro MacBook Pro which has two 6k display outputs.

This is exactly the kind of behavior I'm talking about in my post above.

Your target res of 3008x1692 as a HiDPI resolution is 6016x3384 which is then downscaled to 3840x2160.

The issue seems to be often that Apple limits the size of the frame buffer based on the capabilities of its ports, which is ridiculous. Whether you output native 4K res or 8K downscaled to 4K, the bandwidth requirement is the same as the data sent is equivalent to 4K but the CPU/GPU has to work harder to render and downscale it and more VRAM is used.

Whether HiDPI support triggers or not is also very erratic, as with your DP vs HDMI example. I would not be surprised if you used DP for both displays they would both work just fine for HiDPI scaling.

 

[pshufd]

This is exactly the kind of behavior I'm talking about in my post above.

Your target res of 3008x1692 as a HiDPI resolution is 6016x3384 which is then downscaled to 3840x2160.

The issue seems to be often that Apple limits the size of the frame buffer based on the capabilities of its ports, which is ridiculous. Whether you output native 4K res or 8K downscaled to 4K, the bandwidth requirement is the same as the data sent is equivalent to 4K but the CPU/GPU has to work harder to render and downscale it and more VRAM is used.

Whether HiDPI support triggers or not is also very erratic, as with your DP vs HDMI example. I would not be surprised if you used DP for both displays they would both work just fine for HiDPI scaling.

My only way to fix this would be to get an M1 Max (I have no need for an Ultra) and my production is native 4k so I'm good with only one monitor working in a scaled resolution. It's just a convenience for me to run it in scaled outside of business hours. So I'll just live with it for now and I'll think about a Mac Studio even though the Mac Studio is overkill overall for me. I can well understand the complaints though - it would be nice if Apple explained the limitations of their systems rather than just saying that you can't do that because of the limitations of their hardware and not your monitor. It results in people trying different cables and monitors to solve the problem.

 

[maflynn]

They work just fine with external monitors as long as they have common aspect ratio, high-dpi and modern connectivity.

Monitors come in all forms and sizes and it doesn't matter if it's due to the M1 Mac, or MacOS, its shockingly poor compared against windows machines.

What are these "terrible scaling issues" you speak of? I've used a variety of monitors with zero issues.

I can only speak from my experience, while my 14" MBP's screen is absolutely gorgeous, its scaling is top notch, when I connect it to my 34" ultrawide monitor, the image quality is poor - especially when you compare it against laptops that cost a fraction of the MBP

I'm really happy with my M1 Mac, and its rarely connected to my monitor, but I was shocked at how poor it looked.

 

[pshufd]

This is what it looks like: same system, basically the same monitors, Dell Ultrasharp 4k 27 inches, and three different working scaled resolutions available:

 

[CasualFanboy]

Monitors come in all forms and sizes and it doesn't matter if it's due to the M1 Mac, or MacOS, its shockingly poor compared against windows machines.


I can only speak from my experience, while my 14" MBP's screen is absolutely gorgeous, its scaling is top notch, when I connect it to my 34" ultrawide monitor, the image quality is poor - especially when you compare it against laptops that cost a fraction of the MBP

I'm really happy with my M1 Mac, and its rarely connected to my monitor, but I was shocked at how poor it looked.

Same, man. I just don't even bother connecting this 16" M1 Pro to an external monitor because the visual quality just plummets.

 

[leman]

Monitors come in all forms and sizes and it doesn't matter if it's due to the M1 Mac, or MacOS, it’s shockingly poor compared against windows machines.

Vert true, but it’s not Apples goal to support all possible configurations. They focus on a certain opinionated subset. Macs are a bad choice if you want wide hardware (or software) compatibility, always have been.

 

[Lihp8270]

Vert true, but it’s not Apples goal to support all possible configurations. They focus on a certain opinionated subset. Macs are a bad choice if you want wide hardware (or software) compatibility, always have been.

To phrase this another way.

It’s apples goal to lock out support for affordable quality displays. And force users to buy high value peripherals through intentionally poor support

 

[maflynn]

Vert true, but it’s not Apples goal to support all possible configurations. They focus on a certain opinionated subset. Macs are a bad choice if you want wide hardware (or software) compatibility, always have been.

I gotta say this sounds more like a rationalization and an excuse. Spending a premium amount of money for the laptop, one should expect a premium experience with one's external monitor. We're not talking about arcane hardware but main stream monitors like LG, that are using standard interfaces, like HDMI, DisplayPort and USB-C.

Having an overall poor experience when using an external monitor should not be excused.

 

[leman]

To phrase this another way.

It’s apples goal to lock out support for affordable quality displays. And force users to buy high value peripherals through intentionally poor support

Absolut nonsense. We use M1 Macs with various 4K displays from Dell, LG and Asus and have had no problems. I have an AOC U32U1 at home and it works very well too.

 

[Lihp8270]

Absolut nonsense. We use M1 Macs with various 4K displays from Dell, LG and Asus and have had no problems. I have an AOC U32U1 at home and it works very well too.

I simply reversed your statement.

You said that it’s not apples job to support, and it’s their job to focus on a a subset.

 

[pshufd]

Absolut nonsense. We use M1 Macs with various 4K displays from Dell, LG and Asus and have had no problems. I have an AOC U32U1 at home and it works very well too.

It can work but it depends on what you are trying to do.

My M1 mini is driving 3 4k monitors and 1 QHD monitor and it is doing what I need it to do. But there are a few things that I would like it to do that it can't do. If you're happy with HD or QHD off 4k monitors, then it may work just fine. If you want 3,008 x 1,692, then there are limitations. It would be nice to have a matrix of what works and what doesn't from Apple.

 

[kasakka]

Vert true, but it’s not Apples goal to support all possible configurations. They focus on a certain opinionated subset. Macs are a bad choice if you want wide hardware (or software) compatibility, always have been.

It's Apple's job to support standard display port types and the features offered for those. Until they start posting "only works with this list of monitor models" the expectation is that any display that uses those ports will work as expected. But that is not the reality and there is no excuse for Apple being this bad at it.

 

[Xiao_Xi]

It's Apple's job to support standard display port types and the features offered for those. Until they start posting "only works with this list of monitor models" the expectation is that any display that uses those ports will work as expected.

Apple can choose to improve compatibility with more monitors or create a label for monitors compatible with Apple hardware. Not knowing if a monitor will work is the worst situation.

 

[pshufd]

We could do a thread on what works and what doesn't but I think that's a complicated issue.

 

[kasakka]

We could do a thread on what works and what doesn't but I think that's a complicated issue.

There's this list: https://tonsky.me/blog/monitors-mac/

Unfortunately it's not the most comprehensive.

You can also check Rtings reviews as they test if it works with Macs but they use a higher end M1 so there is no guarantee it will work with older Intel/AMD GPU Macs.

For example my current monitor should work at 4K 144 Hz but my 2019 MBP with Radeon 5300M only outputs 4K 60 Hz.

 

[pshufd]

There's this list: https://tonsky.me/blog/monitors-mac/

Unfortunately it's not the most comprehensive.

You can also check Rtings reviews as they test if it works with Macs but they use a higher end M1 so there is no guarantee it will work with older Intel/AMD GPU Macs.

For example my current monitor should work at 4K 144 Hz but my 2019 MBP with Radeon 5300M only outputs 4K 60 Hz.

Further confusing things is that a monitor may work on one kind of port and not well on another.