Mac mini: 4k @ 120hz?

[marnovo]

I've been researching this for about a year and glad I finally found this thread. At least I know I've exhausted the possibilities apart from ditching macOS.

I've tried about everything obscure to the point I had already given up and "settled" with enough hacks to use my LG CX 48in at half capacity with my MBP 2018 15in (4k @ 60Hz, no HDR, 8bit, but at least 4:4:4 chroma subsampling and no ABL and controlling some of the menus via launcher/CLI).

What sparked again my curiosity if there were any developments around this was the release of new MBPs with 120Hz/VRR and the AORUS 48 monitor (a "repurposed" version of the 48in LG OLEDs, with less features, a lot of issues, BUT with a displayport which makes it work with the new MBPs 4k @ 120Hz according to reports on reddit).

I have little hope of Apple fixing this outside of something released on their own—more likely we'd eventually find an arcane & brittle system-level hack) but worth the joint effort nonetheless.

Reported to Apple with references to the previous feedback tickets posted here. Mine: FB9816919

 

[PieroPontra]

I just set up my 8K TV + 6800 XT. I can confirm it works in Windows 8K 60Hz Full RGB or 4K 120Hz Full RGB but macOS 12.1 is limited to 4K 60Hz as you stated here. It's a shame.

 

[liminalsunset]

Does anyone have a DP dummy plug (those headless ones) from Amazon that cost about 10 bucks that they could open and see what is inside? I'm curious what is inside one of them (and don't necessarily want to buy a 3 pack just to take them apart yet)

The primary theory on this thread seems to be that 1) DisplayPort monitors 4k 120Hz work fine on macOS natively 2) Adapters are passing through monitor's EDID 3) macOS is deciding to not support the signalling even though it works fine on Windows

It appears that DisplayPort EDID is carried by an EEPROM chip that is connected to a few pins of the DisplayPort connector. I am thinking that if we can extract the EDID from a working 4K 120Hz DP monitor using Windows, we can copy the EDID to a headless DP dummy plug to see if it will allow macOS to output at 4k 120Hz.

If this indeed works, maybe it would be possible to buy a DP 1.4 to HDMI adapter, then disconnect the wires related to the EDID and connect them to the dummy plug instead. Then there's a possibility to macOS, it will see the "DP monitor", and just output the signal to the adapter.

 

[liminalsunset]

Actually, theres a bunch of confusing things about whats going on with the CAC adapters, the conversion is supposed to be completely transparent to the graphics card with it believing it should be talking to a DSC enabled display, but the bug title seems off. the protocol clock that DP uses isn't directly related with the pixel clock.

a) DP doesn't itself have a pixel clock, the device doing the protocol conversion is responsible for providing the pixel clock.

b) DP++ passive hdmi output (2.0 max), would be the graphics card (currently adaptable only to 594Mhz by design and specification)

c) HDMI 2.1 does not use TMDS, so the pixel clock is irrelevant (the only reason the resolution creator even mentions it is a legacy hdmi holdover).

For whatever reason, the adapter is not reporting dsc capability to the driver unless the tv supports the hdmi 2.1 dsc spec.

Club3D should patch their firmware to spoof DSC support from the TV end. https://forums. guru3d.com/members/astyanax.273678/

I found this information from https://forums. guru3d.com/threads/what-changes-did-nvidia-make-to-hdcp-or-dsc-a-few-drivers-back-who-is-at-fault.436677/page-2.

According to this, the pixel clock theory might not actually be accurate here. Perhaps this is something that is actually the adapter's job to deal with. Maybe someone with the CAC 1586 adapter can email support and inquire, since they have put out updates to fix problems before and I'd expect faster response than from Apple.

 

[joevt]

I found this information from https://forums. guru3d.com/threads/what-changes-did-nvidia-make-to-hdcp-or-dsc-a-few-drivers-back-who-is-at-fault.436677/page-2.

According to this, the pixel clock theory might not actually be accurate here. Perhaps this is something that is actually the adapter's job to deal with. Maybe someone with the CAC 1586 adapter can email support and inquire, since they have put out updates to fix problems before and I'd expect faster response than from Apple.

I think the people in that thread don't know that a DisplayPort to HDMI adapter will identify itself as an HDMI adapter ("DVI/HDMI Branch") and that could be what triggers the driver to incorrectly limit the output to HDMI 2.0 modes. The information is in the DPCD registers. There are many DPCD registers. The AGDCDiagnose command in macOS reports some of them.
https://forums.macrumors.com/thread...ransfers-recommendation.2278473/post-29466205

 

[scottlilo]

Chiming in to show support for this issue. I would really love to get 4k 120hz working between my M1 Max and LG CX 48"

I really love this laptop, but it is so frustrating that I cannot use my 120hz display to it's full potential.

Crossing my fingers that Apple can release a software fix for these issues.

 

[dcheatz20]

Looking more into it I ran into a site that lists mac and monitor combinations that work at 4K @ 120hz

Macs and 4K 120Hz displays compatibility list

Macs/4K 120Hz displays compatibility list

tonsky.me

 

[scottlilo]

I have reached out to HDfury on Discord who created the Dr HDMI 8k (reprogrammable EDID Manager) and he was kind enough to provide these values for testing, if anyone has an EDID Manager, he suggests giving this a try with a `DP -> HDMI Adapter`

the attached file is an EDID file that can be loaded into any EDID manager (From Dr HDMI, or any other)


I was hoping that the Dr HDMI 8k could be used to spoof the EDID/Timings needed to run 4k 120hz through an adaptor, but he is unsure at this point if this would be possible with his device.

I am in over my head here, but grasping at straws in attempt to help get this effort moving. I hope this is of use to someone.

 

[PieroPontra]

You know what? I'm using my 6800 XT + Samsung TV as like: 7680x4320 60Hz 10 bit RGB 4:4:4 FreeSync SDR and it's glorious! Obviously in windows 11 since macos is a shame at the moment. You can't even use VRR / Freesync on HDMI regardless of resolution etc... just on DisplayPort. I simply connected an HDMI 2.1 cable et voilà! I've used macOS since 15 years... now it's about a week that I'm using Win 11 exclusively.

 

[brdtoledo]

You know what? I'm using my 6800 XT + Samsung TV as like: 7680x4320 60Hz 10 bit RGB 4:4:4 FreeSync SDR and it's glorious! Obviously in windows 11 since macos is a shame at the moment. You can't even use VRR / Freesync on HDMI regardless of resolution etc... just on DisplayPort. I simply connected an HDMI 2.1 cable et voilà! I've used macOS since 15 years... now it's about a week that I'm using Win 11 exclusively.

Same here. I'm switching to Windows 11.

 

[Artagra]

I have reached out to HDfury on Discord who created the Dr HDMI 8k (reprogrammable EDID Manager) and he was kind enough to provide these values for testing, if anyone has an EDID Manager, he suggests giving this a try with a `DP -> HDMI Adapter`

the attached file is an EDID file that can be loaded into any EDID manager (From Dr HDMI, or any other)


I was hoping that the Dr HDMI 8k could be used to spoof the EDID/Timings needed to run 4k 120hz through an adaptor, but he is unsure at this point if this would be possible with his device.

I am in over my head here, but grasping at straws in attempt to help get this effort moving. I hope this is of use to someone.

Just ordered one - I looked into "HDMI Pass-Through EDID Emulators" but hadn't found one that looked promising, but this Dr HDMI 8k does.

Thanks for the info! I will try it and report back.

For anyone else interested:

Dr HDMI 8K | HDFury.com | Connect and Fix everything in HDMI

World First HDMI 2.1 EDID Manager with webserver and Android/iOS APP! Up to FRL5/40Gbps/1200MHz signal passthru with VRR support + FRL6/48Gbps/1500MHz under testing The Dr.HDMI 8K Kit includes: Dr.HDMI 8K unit Choice of power supply USB power cable (6ft)

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[Monstieur]

I have reached out to HDfury on Discord who created the Dr HDMI 8k (reprogrammable EDID Manager) and he was kind enough to provide these values for testing, if anyone has an EDID Manager, he suggests giving this a try with a `DP -> HDMI Adapter`

the attached file is an EDID file that can be loaded into any EDID manager (From Dr HDMI, or any other)


I was hoping that the Dr HDMI 8k could be used to spoof the EDID/Timings needed to run 4k 120hz through an adaptor, but he is unsure at this point if this would be possible with his device.

I am in over my head here, but grasping at straws in attempt to help get this effort moving. I hope this is of use to someone.

I have an 8K VRROOM and this will not fix the problem. HDFury did not understand the issue in the Discord channel. They don't believe that DisplayPort 1.4 to HDMI 2.1 is possible on a MBP in the first place, which is clearly wrong as the adapter works on Windows on the same MBP.

A custom EDID on a downstream device cannot change the DCDP registers reported by the adapter. The 8K VRROOM will still report as a HDMI device.

The only fix would be reverse engineering a patch, new firmware from the adapter manufacturers, or support from Apple for what is technically non-standard HDMI.

 

[Monstieur]

I now have a separate issue now where my LG G1 no longer works with my MBP on macOS 12.1. It wasn't due to the update to 12.1 as it worked for a few days after that.

It displays the macOS desktop for a few seconds and goes blank (i.e. macOS sends a black screen). I can see on the TV and the VRROOM that there is in fact a 4K 60 Hz RGB 8-bit FRL2 signal. If I change the resolution, the image comes back for a few seconds and goes blank again, and the TV / VRROOM continue to report the new resolution. I know it's macOS sending a blank screen because if I use YCbCr420, the TV turns grey with raised black levels instead of black.

This happens with the HDMI 2.1 adapter as well as Apple's AV adapter (which is limited to 2560x1440) on the LG G1.

When I upgraded to macOS 12.0, HDMI audio stopped working. No sound plays when using the DisplayPort audio device. Now the video is dead too.

 

[PieroPontra]

I can confirm 8K 60hz doesn work too, not with a direct HDMI 2.1 connection and not with a USB-C DP Alt Mode to HDMI 2.1 Both work in windows, but full fledged with direct 2.1 cable and limited with the adapter. I suspect 6800xt usb c port doesn’t support DSC. This is a big mess, Apple should just support 2.1 natively at this point.

 

[Monstieur]

I can confirm 8K 60hz doesn work too, not with a direct HDMI 2.1 connection and not with a USB-C DP Alt Mode to HDMI 2.1 Both work in windows, but full fledged with direct 2.1 cable and limited with the adapter. I suspect 6800xt usb c port doesn’t support DSC. This is a big mess, Apple should just support 2.1 natively at this point.

8K 60 Hz RGB requires DSC on both the DisplayPort and HDMI side. These adapters support DSC on the DisplayPort side, but I'm not sure if they do on the HDMI side. LG TVs don't support DSC anyway so they can't do 8K 60 Hz RGB.

 

[PieroPontra]

What’s the purpose in supporting “half DSC” ? Why should you let DSC in without letting it pass through?

LG Nanocell 8K doesn’t, but MiniLED QNED should. Anyway I got a MiniLED Samsung and in Windows it’s fine

 

[joevt]

What’s the purpose in supporting “half DSC” ? Why should you let DSC in without letting it pass through?

LG Nanocell 8K doesn’t, but MiniLED QNED should. Anyway I got a MiniLED Samsung and in Windows it’s fine

For a DisplayPort 1.4 to HDMI 2.1 adapter, you have two sides:
DisplayPort input: 12.96, 25.92 Gbps (for 2 lanes or 4 lanes of HBR3 link rate)
HDMI 2.1 output: 8.16, 14.40 Gbps (for TMDS at 3 or 6 Gbps per lane, 3 lanes) or 21.33, 28.44 35.56 42.67 Gbps (for FRL at 6, 8, 10, or 12 Gbps per lane, 4 lanes)

You see that the max for DisplayPort (25.92 Gbps) is not going to achieve the max for HDMI (42.67 Gbps).
DSC can reduce the bpp from 30 (for HDR) down to 8 (though Apple uses a default of 12 bpp for DSC but you can override that).

Now if your adapter accepts DSC at the input and decompresses that for the output (so no DSC for the output), then it can basically turn the 25.92 Gbps of DisplayPort into 42.67 Gbps of HDMI 2.1 using DSC. We can calculate the best DSC bits per pixel target like this:

input bandwidth / output bandwidth * output bits per pixel
For 30 bpp output, you need DSC @ 18.22 bpp.
For 24 bpp output, you need DSC @ 14.58 bpp.

However, HDMI 2.1 can't do 8K60 without using either DSC (12g:17bpp; 10g:14bpp; 8g:11bpp; 6g:8bpp) or chroma sub sampling (12g: 4:2:2 8bpc, 4:2:0 10bpc; 10g: 4:2:0 8bpc)
so if the adapter can't recompress the input, then you want it to at least pass through the DSC.
Is DisplayPort DSC close enough to HDMI DSC so that an adapter doesn't need recompress to go from one to the other?

 

[PieroPontra]

For a DisplayPort 1.4 to HDMI 2.1 adapter, you have two sides:
DisplayPort input: 12.96, 25.92 Gbps (for 2 lanes or 4 lanes of HBR3 link rate)
HDMI 2.1 output: 8.16, 14.40 Gbps (for TMDS at 3 or 6 Gbps per lane, 3 lanes) or 21.33, 28.44 35.56 42.67 Gbps (for FRL at 6, 8, 10, or 12 Gbps per lane, 4 lanes)

You see that the max for DisplayPort (25.92 Gbps) is not going to achieve the max for HDMI (42.67 Gbps).
DSC can reduce the bpp from 30 (for HDR) down to 8 (though Apple uses a default of 12 bpp for DSC but you can override that).

Now if your adapter accepts DSC at the input and decompresses that for the output (so no DSC for the output), then it can basically turn the 25.92 Gbps of DisplayPort into 42.67 Gbps of HDMI 2.1 using DSC. We can calculate the best DSC bits per pixel target like this:

input bandwidth / output bandwidth * output bits per pixel
For 30 bpp output, you need DSC @ 18.22 bpp.
For 24 bpp output, you need DSC @ 14.58 bpp.

However, HDMI 2.1 can't do 8K60 without using either DSC (12g:17bpp; 10g:14bpp; 8g:11bpp; 6g:8bpp) or chroma sub sampling (12g: 4:2:2 8bpc, 4:2:0 10bpc; 10g: 4:2:0 8bpc)
so if the adapter can't recompress the input, then you want it to at least pass through the DSC.
Is DisplayPort DSC close enough to HDMI DSC so that an adapter doesn't need recompress to go from one to the other?

Actually I don't know if something like this exists (both input / output DSC) but elaborating your post I think our best bet is achieving 8K 60Hz 4:2:2 8 bit which should be ok while waiting for a proper support by Apple of HDMI 2.1 - Am I right or am I missing something? That said, it's not clear if USB-C port of RX 6000 cards support DSC... on AMD website it is clearly stated for full size DP ports but not for USB-c and in any case the adapter in Windows is not giving 8K 60Hz so I think it's not DSC output compatible. Anyway the amount of variables in this situation is so high that I can't really tell what's going on here...

Should we focus on achieving 8K 60Hz 4:2:2 8 bit? Maybe I have to give the sabrent usb-c adapter ine more try before returning it? Is still whatevergreen our best hope ? Feel free to tell me exactly what to do at this point and I'll do anything you need me to do.

 

[joevt]

Actually I don't know if something like this exists (both input / output DSC) but elaborating your post I think our best bet is achieving 8K 60Hz 4:2:2 8 bit which should be ok while waiting for a proper support by Apple of HDMI 2.1 - Am I right or am I missing something?

8 bpc is not good enough for HDR but if you don't care about HDR then that's ok.

The problem is, I said 8K60 4:2:2 8bpc only works for the highest speed HDMI 2.1 (12Gbps per lane, 48 Gbps total on the wire, ≈42.67 Gbps of actual data) but. according to the EDID of the Samsung Q900A, it only supports FRL up to 10 Gbps (40 Gbps total on the wire, ≈35.56 Gbps of actual data) so it would require 4:2:0 but it can do 10bpc at that level of chroma sub sampling.

Well actually, if you reduce the pixel clock to 2090 MHz using CVT-RB calculation (down from the normal 2376 MHz of HDMI) then 4:2:2 8bpc is possible. We already know that the Q900A can do 4:2:0 at 2090 MHz. But I haven't seen 4:2:2 8bpc get tried yet. A test in Windows might be sufficient since the Radeon software should let you choose 4:2:2 and 8bpc if that combination is possible. The log show output from #181 doesn't show if any 422 modes are accepted in macOS. Maybe output from the AllRez command #177 might show some 422 modes having been accepted by macOS?

That said, it's not clear if USB-C port of RX 6000 cards support DSC... on AMD website it is clearly stated for full size DP ports but not for USB-c and in any case the adapter in Windows is not giving 8K 60Hz so I think it's not DSC output compatible. Anyway the amount of variables in this situation is so high that I can't really tell what's going on here...

There's no reason for the USB-C port to not have all the DisplayPort capabilities of the other ports.

 

[PieroPontra]

8 bpc is not good enough for HDR but if you don't care about HDR then that's ok.

The problem is, I said 8K60 4:2:2 8bpc only works for the highest speed HDMI 2.1 (12Gbps per lane, 48 Gbps total on the wire, ≈42.67 Gbps of actual data) but. according to the EDID of the Samsung Q900A, it only supports FRL up to 10 Gbps (40 Gbps total on the wire, ≈35.56 Gbps of actual data) so it would require 4:2:0 but it can do 10bpc at that level of chroma sub sampling.

Well actually, if you reduce the pixel clock to 2090 MHz using CVT-RB calculation (down from the normal 2376 MHz of HDMI) then 4:2:2 8bpc is possible. We already know that the Q900A can do 4:2:0 at 2090 MHz. But I haven't seen 4:2:2 8bpc get tried yet. A test in Windows might be sufficient since the Radeon software should let you choose 4:2:2 and 8bpc if that combination is possible. The log show output from #181 doesn't show if any 422 modes are accepted in macOS. Maybe output from the AllRez command #177 might show some 422 modes having been accepted by macOS?


There's no reason for the USB-C port to not have all the DisplayPort capabilities of the other ports.

SDR mode (HDR Off in Windows)

HDR On

These are the infos Win 11 shows in SDR and HDR mode. Please note:

1. In SDR mode the TV reports 7680x4320 60Hz Freesync Premium Pro
2. To achieve such high resolution / refresh you must turn on Input Signal Plus (trading compatibility for higher bandwidth)
3. In Windows 11 HDR mode on, the TV doesn't automatically switch to HDR mode and still reports 7680x4320 60Hz Freesync Premium Pro
4. I don't know if Windows is saying RGB 4:4:4 but in reality the TV is going 4:2:0 I think there's no way to check subsampling on Samsung software

All of this achieved using direct HDMI 2.1 connection between GPU and 8K TV.

Speaking of the USB-C DP Alt Mode port on the GPU, something I think it's limiting it. If you say that's impossible it doesn't support DSC since the standard DP ports do... well then it must be the USB-C to HDMI 2.1 Sabrent adapter causing the issue (?!). Sabrent clearly states their adapter supports DSC but as soon as I connect it to the usb-c port of the gpu and use the same 48gbps cable to connect it to the same HDMI port of the tv I only got 8K 30Hz 4:2:0 8 bit and nor Win 11 nor AMD software allow me to go any higher and I also loose VRR Freesync.

 

[frisbfreek]

For what it’s worth, I hear the Club3D adapters are supposed to support DSC input to non-DSC output (decompressing) as well as DSC pass through. I can’t say about the rest of the DP -> HDMI and USB-C -> HDMI adapters though (might be worth asking).

 

[frisbfreek]

Perhaps to help debug, which dumbed down 8K resolutions does M1/MacOS support?

1. 8K 30hz 4:2:0 8-bit
2. 8K 30hz 4:4:4 8-bit
3. 8K 60hz 4:2:0 8-bit
4. 8K 30hz 4:4:4 10-bit

#1 has the same bandwidth as 4K 60hz 4:4:4, so if it doesn’t work then there’s a driver limitation (especially since M1 macs are advertised to only support 6K) and not a bandwidth issue.

#2 and #3 presumably should have the same bandwidth requirements (capable under DisplayPort 1.4 without DSC).

#4 exceeds DisplayPort 1.4 without DSC, so if #2 works but #4 does not, then it’s a DSC issue.

 

[PieroPontra]

Perhaps to help debug, which dumbed down 8K resolutions does M1/MacOS support?

1. 8K 30hz 4:2:0 8-bit
2. 8K 30hz 4:4:4 8-bit
3. 8K 60hz 4:2:0 8-bit
4. 8K 30hz 4:4:4 10-bit

#1 has the same bandwidth as 4K 60hz 4:4:4, so if it doesn’t work then there’s a driver limitation (especially since M1 macs are advertised to only support 6K) and not a bandwidth issue.

#2 and #3 presumably should have the same bandwidth requirements (capable under DisplayPort 1.4 without DSC).

#4 exceeds DisplayPort 1.4 without DSC, so if #2 works but #4 does not, then it’s a DSC issue.

I think it's already been proved that's a driver limitation, since the same exact hardware works in Windows (as example, RDNA 2 cards in Mac Pros 2019. They introduced Adaptive Sync in macOS 12.1 but only for DisplayPort... plain Apple Style.

 

[mfractal]

Just ordered one - I looked into "HDMI Pass-Through EDID Emulators" but hadn't found one that looked promising, but this Dr HDMI 8k does.

Thanks for the info! I will try it and report back.

For anyone else interested:

Dr HDMI 8K | HDFury.com | Connect and Fix everything in HDMI

World First HDMI 2.1 EDID Manager with webserver and Android/iOS APP! Up to FRL5/40Gbps/1200MHz signal passthru with VRR support + FRL6/48Gbps/1500MHz under testing The Dr.HDMI 8K Kit includes: Dr.HDMI 8K unit Choice of power supply USB power cable (6ft)

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Please keep us updated once you receive it. it does look promising.

 

[Monstieur]

Please keep us updated once you receive it. it does look promising.

I have one. It cannot address this problem.