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fayzaan

macrumors newbie
Original poster
Nov 16, 2022
5
0
I have tried to search on this forum and on the web but I cannot seem to find any answers to this.

I understand under the hood Mac is using HDMI 2.0 spec, according to that the maximum HDMI 2.0 can support is 4k @ 60Hz. I have a Samsung Neo G9 ultra-wide monitor (5120x1440, which is technically less than 4k).

When I try to use the Macbook with G9 monitor over HDMI to HDMI or HDMI to USB-C, the maximum resolution available is 3840x1080. Even if I try toggling "Show all resolutions". I already manually lowered the refresh rate to 60Hz via the Monitor settings. I have tested the HDMI to HDMI cable with my PC and can confirm it works fine at 4k 120Hz (HDMI 2.1 on PC), so 4k 60Hz should work on the mac.

If I use a DP (DisplayPort) to USB-C, I am able to get the 5120x1440 resolution, but I have reserved the DP for my PC because I need the extra refresh rate for that, I don't really care for high refresh rate on the Mac, so I want to run that off the HDMI.

Why can't I get the 5120x1440 at 60Hz resolution option over HDMI?
 

casperes1996

macrumors 604
Jan 26, 2014
7,523
5,692
Horsens, Denmark
I can't say why, but I can say that you can use a USB-C->HDMI cable to get HDMI 2.1 on the Mac that will probably make it work even though 2.0 bandwidth wise should be fine
 

fayzaan

macrumors newbie
Original poster
Nov 16, 2022
5
0
Yea, I have tried that as well - tried both HDMI 1 and HDMI 2 port on monitor with a HDMI to USB-C cable. Even the monitor alerts me to use the recommended 5120x1440 @ 60Hz resolution. But the option to select 5120x1440 is not available from the Mac's Display Settings.

Screen Shot 2022-11-16 at 10.08.39 AM.png


When I go to the Settings from the Monitor itself, I can set to 60Hz but regardless I don't get a 5120x1440 option from Mac's Display Settings.
 

casperes1996

macrumors 604
Jan 26, 2014
7,523
5,692
Horsens, Denmark
Hm. This makes me think the display might be sending wrong EDID/DisplayID information to the Mac when connected via HDMI on the display end, incorrectly telling the Mac that its native resulotuoin is 3840x1080

You can try getting an EDID dump. The first answer here is a good guide

With my Home-brew setup I changed the BINDIR and MANDIR to /usr/local/bin and /usr/local/share/man respectively. For Apple Silicon Home-brew is in opt instead of local IIRC. But you don't have to install the program. You can keep it in its dir and just run it from there instead
 

fayzaan

macrumors newbie
Original poster
Nov 16, 2022
5
0
Ok, so I couldn't find anything using the ioreg commands they were using, but I ran `ioreg -l | grep EDID` and got this info:

The ProductName does match the monitor in question and according to this the native resolution is wrong, 3840x1080. Is there a way to change this or override to use the proper resolution?

JSON:
{
  "SupportsSuspend""=No",
  "MaximumRefreshRate"=75,
  "SupportsActiveOff""=No",
  "PortID"=0,
  "ProductAttributes""="{
    "ManufacturerID""=""SAM",
    "YearOfManufacture"=2022,
    "SerialNumber"=809719885,
    "ProductName""=""LS49AG95",
    "AlphanumericSerialNumber""=""HCST400146",
    "LegacyManufacturerID"=19501,
    "ProductID"=29098,
    "WeekOfManufacture"=14
  },
  "MaxVerticalImageSize"=34,
  "MaxHorizontalImageSize"=119,
  "HasHDMILegacyEDID""=No",
  "Chromaticity""="{
    "Red""="{
      "X"=45504,
      "Y"=19200
    },
    "Green""="{
      "X"=17984,
      "Y"=43200
    },
    "Blue""="{
      "X"=9728,
      "Y"=3712
    }
  },
  "DefaultColorSpaceIsSRGB""=No",
  "NativeFormatHorizontalPixels"=3840,
  "DefaultWhitePoint""="{
    "X"=20544,
    "Y"=21568,
    "Gamma"=144179
  },
  "SupportsVariableRefreshRate""=No",
  "AspectRatio"=0,
  "MinimumRefreshRate"=50,
  "WhitePoints""=("{
    "X"=20544,
    "Y"=21568,
    "Gamma"=144179
  }")",
  "PreciseAspectRatio"=229376,
  "ContinuousFrequencySupport""=""None",
  "SupportsStandby""=Yes",
  "NativeFormatVerticalPixels"=1080
}
 

fayzaan

macrumors newbie
Original poster
Nov 16, 2022
5
0
No, unfortunately that solution does not work for me. It only allows me to select the resolutions already listed in the mac Display Settings. I did try adding a custom resolution but that did not work, and I cannot change my resolution through the app - Maybe has to do with this being an Apple Silicon or something.

I found some instructions here https://apple.stackexchange.com/que...oesnt-work-at-full-resolution-with-my-macbook

for overriding the display settings to allow the proper native resolution but seems to be a risky solution..
 

HobeSoundDarryl

macrumors G5
SwitchResX is all about overriding default Mac Res settings (actually unhiding what can be done that Apple chooses NOT to show in the Preferences, Display tool)… and I can share first hand that it works very well with Silicon.

I have a 5120 X 2160 ultra wide and found it ideal for targeting a resolution well above that (7680 X 3240) to then give me a hidpi resolution of 3840 X 1620 at 60Hz for typical uses with an easy, one-click option to flip to full res for select apps that can benefit from small os elements but max horizontal RE. A difference is that I'm connecting to the Thunderbolt port on my UW, not HDMI.

You might want to dig a bit deeper into what you can do with it. Your solution is prob there.

Unfortunately, the HDMI "demand" may be central to your challenge. Perhaps look into a hub that will let both the PC and Mac "share" the DisplayPort/USB-C connection: PC and Mac into Hub, Hub "out" into monitor? This would be analogous to a home theater setup with multiple video sources feeding their signal via HDMI into a receiver (the hub in this analogy) and then a single cable "out" from that "hub" to the TV screen.

A quick test to perhaps put some fuel towards this concept would be to use the SAME HDMI cable not working as you wish with that Mac to connect the PC in the same way. Then see if you can get 5120 X 1440 resolution as you seek it from the PC via HDMI. If:
  • yes, SwitchResX should give you a way from the Mac using that same cable to HDMI connection.
  • not, I suspect cable or HDMI port limitation. Testing another cable is easy enough (be sure it’s a good, robust one). If that doesn't deliver, the "middleman" hub concept is probably THE way to get what you want.
I hope this is helpful.
 
Last edited:

zorinlynx

macrumors G3
May 31, 2007
8,242
18,068
Florida, USA
Sadly Apple didn't spec the HDMI port on the M1 Macbook Pros as high as they could have. I *STRONGLY* suspect they only added the HDMI port as a second thought and didn't put much effort into implementing the best HDMI port they could.

This isn't the first time; even the $6000 Intel Mac Pro suffers from this! We purchased one at work and only had an HDMI cable to plug it into the monitor we got, it couldn't drive the monitor at full resolution until the USB-C to DP cable came in and we started using that.
 

joevt

Contributor
Jun 21, 2012
6,769
4,103
DisplayPort to HDMI adapters should be able to do width 5120. The M1 MacBook Pro might have one of those (limited to HDMI 2.0 bandwidth which is < 600 MHz pixel clock for 8bpc RGB).

HDMI to DisplayPort/USB-C adapters can't do > 4K width unless they use the new converter chips that support HDMI 2.1, such as the CAC-1335 or CAC-1336. Which such converter chip, even HDMI 2.0 can do width up to 5K.
https://insights.club-3d.com/thread/cac-1336-operation/

The problem with M1/M2 Macs is that while they may allow adding custom scaled modes (with SwitchResX), they don't seem to support custom timings (which can be added using SwitchResX and work for Intel Macs). Perhaps something like the Dr HDMI 8K can override the EDID and allow custom timings that way, but that would be limited to HDMI 2.0 bandwidth. Maybe a DisplayPort 1.4 to HDMI 2.1 adapter with a Dr HDMI 8K can exceed that limit.
 

bryo

macrumors member
Apr 6, 2021
73
101
I have tried to search on this forum and on the web but I cannot seem to find any answers to this.

I understand under the hood Mac is using HDMI 2.0 spec, according to that the maximum HDMI 2.0 can support is 4k @ 60Hz. I have a Samsung Neo G9 ultra-wide monitor (5120x1440, which is technically less than 4k).

When I try to use the Macbook with G9 monitor over HDMI to HDMI or HDMI to USB-C, the maximum resolution available is 3840x1080. Even if I try toggling "Show all resolutions". I already manually lowered the refresh rate to 60Hz via the Monitor settings. I have tested the HDMI to HDMI cable with my PC and can confirm it works fine at 4k 120Hz (HDMI 2.1 on PC), so 4k 60Hz should work on the mac.

If I use a DP (DisplayPort) to USB-C, I am able to get the 5120x1440 resolution, but I have reserved the DP for my PC because I need the extra refresh rate for that, I don't really care for high refresh rate on the Mac, so I want to run that off the HDMI.

Why can't I get the 5120x1440 at 60Hz resolution option over HDMI?
I have a guess. It is a limitation of the HDMI port in the G Sync module. I have a similar issue where my alienware ultrawide cant support full 100hz over hdmi, and defaults to 50. I'm guessing its a similar limitation on the gsync module on the neo g9. You could try plugging your pc in via hdmi to see if that is actually the issue or not.
 

fayzaan

macrumors newbie
Original poster
Nov 16, 2022
5
0
I would be ok with 50Hz or maybe even 30Hz at 5120x1440. This connection is primarily for work, I have a PC which I want to use for gaming at 240Hz via DP. HDMI is too weak to support such resolution with such high Hertz.

I don’t understand why Samsung only included 1 DP and 2 HDMI 2.1 when HDMI 2.1 can’t even drive 240Hz with 5120x1440. And afaik DP can only do it using DSC.

So I think the easiest route is to get some displayport extension cable and just swap between the mac/pc.

KVM might be an option but I think it will just add complication to the setup and potentially not work at 240hz 5120x1440 on pc.

Thanks for all the help
 

HobeSoundDarryl

macrumors G5
There's a LOT of these kinds of little boxes on Amazon and similar. Maybe shop for the ideal specs and try that kind of "middleman" box.
  • PC in DP1.
  • Mac in DP2.
  • DP out to the monitor.
Push the button to switch which computer is connecting to the monitor. There is probably one to be found that will give you exactly what you want to "push" the ideal signal (and speed) to the one jack on the monitor.

613Ej8GUQtL._AC_SL1500_.jpg
 

akevit

macrumors newbie
Aug 3, 2023
1
0
I've only seen those little boxes support 8k@60Hz. When you increase the refresh rate to 120hz there is tearing and artifacts on the screen
 
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