Mac Pro (and Macs in general) incapable of driving 8k displays that use HDMI? Is there some solution?

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Mac Pro (and Macs in general) incapable of driving 8k displays that use HDMI? Is there some solution?

So it's kind of crazy, apple is now tasting 8k work flows, but basically you cannot drive an 8k display on a Mac via HDMI.

Currently the only way you can kind of get an 8k display to work is if you buy an 8k monitor with the now old DisplayPort 1.4 port in it. However, all the new 8k devices have HDMI 2.1 as inputs.

And this isnt a problem with the Mac ports. For example, I have a Mac Pro with an AMD 6900XT that has USB-C, HDMI 2.1 and DisplayPort 1.4 ports. If I hook them into my 8k tv (a Samsung with HDMI 2.1 ports), the most the TV will show is 4k despite having the right cables (like an HDMI 2.1 to HDMI 2.1 cable).

So despite a large number of cards that support 8k output, the Mac cannot send a signal to drive those monitors and TVs. The funny thing is, the Mac will actually MAKE an 8k frame buffer (if you do a screen shot, you get an 8k resolution screenshot), but it pushes that 8k desktop to the monitor with only 4k of resolution, so it looks all garbled and blurry.

It seems this is an issue with Apple's drivers as best as I can tell.

What is weird is even if you use USBc to HDMI 2.1 or DisplayPort1.4 to HDMI2.1 cables, it still wont work. It will only work if you use the lame 30" dell 8k monitor with DisplayPort inputs, but not a single modern 8k tv/monitor with HDMI 2.1 port works.

Is there a solution to this? I need 8k work flows and you know ACTUAL DISPLAY to 8k output devices, but it seems this is impossible to with macOS (and works fine under windows).

Thanks for any help!

Mac Pro, macOS 12.1

Posted on Dec 19, 2021 12:00 AM

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Answer 1

Dec 19, 2021 7:54 AM in response to jkheit

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences (from another display)

When a very large display such as that Samsung is queried, Readers report that a typical default answer is a two-port resolution -- the response provides the resolution for the FIRST connection, then you must connect again with a second cable to get the resolution for the second connection.

You may be able to go higher on a BUILT-IN HDMI port such as on your RX 6900 XT by fiddling with the display profiles using a well-respected third-party tool such as SwichResX.

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Answer 2

Dec 19, 2021 6:26 AM in response to jkheit

The HDMI ports used in the Mac support at most HDMI 2.0, which can support a 4K display at up to 60 Hz. Going to a higher resolution an the Mac requires that you connect DIRECTLY with ThunderBolt, USB-C or DisplayPort, and not attempt to force the DisplayPort into Dual Mode and use an converter.

What display are you talking about that only features HDMI inputs? How many inputs are available?

Many displays with HDMI only inputs can be connected using two cables. The Mac uses Extended Desktop, and the display uses Picture-By-Picture to re-assemble a coherent picture on the display screen.

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Answer 3

jkheit Author

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Dec 20, 2021 2:39 PM in response to Grant Bennet-Alder

Unfortunately, the Samsung does not have a Picture By Picture mode. It has something called Multiview

https://downloadcenter.samsung.com/content/UM/202109/20210930143505633/OSNDVBADA-7.1.0_EM_OSCAR_ASIA_ENG_210709.0.pdf

Page 84 of the manual.

Basically it has Picture in Picture, and oblong asymmetrical windows side by side for multiple sources, but none where you could put 2 modes side by side in some split view that would work as a monitor.

This might have been a nice hack to get around it, but frankly, Apple should be able to use a single cable to drive 8k. I have an 8k supported video card with HDMI 2.1 port, a TV with an HDM 2.1 port, and a 48gbps HDMI 2.1 cable. This should work and for some reason, apple will not output anything but what seems to be an HMDI 2.0 output along that cable. Worse yet, even if use other ports like DisplayPort 2.1 or USBc which also can handle the 8k resolution, it just sabotages the signal. There really is no excuse for this. If apple asserts it supports 8k work flows, and fundamentally prevents you from ever seeing an 8k display, it's pretty much misleading advertising.

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Answer 4

jkheit Author

Level 1

5 points

Dec 19, 2021 6:41 AM in response to Grant Bennet-Alder

The display is this;

https://www.samsung.com/us/televisions-home-theater/tvs/samsung-neo-qled-8k/85-qn900a-neo-qled-8k-smart-tv-2021-qn85qn900afxza/

the vide card I have is these:

https://www.sonnetstore.com/collections/egpu-card-bundles/products/2019-mac-pro-gpu-bundle

https://www.amd.com/en/products/professional-graphics/radeon-pro-wx-9100

both have display port 1.4 which should be able to drive 8k, and the 6900xt also has a usbc port and an in fact has an hdmi 2.1 port. Many Apple Card’s have DisplayPort 1.4 and should support 8k, but if you use an hdmi monitor, apple fails to properly send the 8k signal.

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Answer 5

jkheit Author

Level 1

5 points

Dec 19, 2021 3:16 PM in response to Grant Bennet-Alder

I am using SwitchResX. My card and my TV are both capable and have HDMI2.1 and are capable of 8k@60hz. So is the cables I'm using. It should work on just the one 48gbps cable. What happens is Apple's driver is incapable of sending an 8k signal via HDMI because, my guess is, their drivers are incompetently not up to date and simply ignore the 8k capabilities via HDMI2.1.

I would be happy to get it working 2 cables, but I'm not sure what you mean by it. I dont think the Samsung can use 2 cables to make one composite display, but I'd be happy to try that. So you suggest that I use maybe the 2 DisplayPort 1.4 ports on my video card, and plug them into 2 HDMI ports on the Samsung, and the Samsung will magically pool those two into one composite screen?

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Answer 6

Dec 19, 2021 4:17 PM in response to jkheit

In the display, Picture-By-Picture (variant of Picture-In- Picture, where another input appears in a smaller window). Samsung did not call that out in their specs, but they may have another name for it.

---------

MacOS "Extended Desktop":

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Answer 7

jkheit Author

Level 1

5 points

Dec 20, 2021 3:44 PM in response to Grant Bennet-Alder

Thats bs. It works with ancient display ports that are only supported on like 2 or 3 ~30" displays. Which is actually useless for workflows, since we will be outputting media to, wait for it, televisions. And ALL the 8k TVs out there support... wait for it... only HDMI.

HDMI is not the outlier for 8k, it is the STANDARD for 8k. Also, HDMI 2.1 is 48gbps bandwidth, while display port 1.4 is limited to 32.4gbps, and frankly is more limited, because it's old and tired.

So false. My TV is not the outlier, it is the standard. Go and look at all the 8k TVs out there, they are all HDMI, not display port. Again, the only things that support 8k DisplayPort are old 30" displays, which are USELESS for 8k work flows, because I want to see what the person will actually see on their TV, on 65"/85" output devices.

So again, their claim for 8k workflow is totally bs.

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Answer 8

Dec 20, 2021 3:02 PM in response to jkheit

<< Apple should be able to use a single cable to drive 8k >>

Apple CAN and DOES work with 8K workflows over high-end displays. Your TV set is an outlier in that it only has HDMI inputs.

HDMI is troublesome because it has only three data pathways, and its 5 Volt signals are harder to switch as fast as lower voltages.

DisplayPort has four data pathways, and uses lower voltages, so it is easier to switch it faster, and easier to get it to support higher resolutions.

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Mac Pro (and Macs in general) incapable of driving 8k displays that use HDMI? Is there some solution?

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