Macbook Pro M5Pro missing resolutions and refresh rate on external monitor

Hello again andree. I don't know if you'll ever see this, but if you do, could you please give it a try?

I may have a theory about your 45GX950A being capped at 100 Hz.

I checked the manual of the 45GX950A. It only supports 5K2K at 165 Hz, 100 Hz and 60 Hz. There's no 120 Hz option. And we know that at least 120 Hz is required to enable 3860x1680 HiDPI layout.

Now, the question is why 165 Hz doesn't show up with the latest M5 Pro using TB5. The only difference between M5 Pro and M3 Pro is that the M5 Pro's TB5 connector supports DisplayPort 2.1, whereas TB4 on M3 Pro only supports DP 1.4 with DSC.

One possible explanation is that the downgraded DP 2.1 54 Gbps bandwidth version (commonly used by LG) may not be sufficient for 5K2K at 165 Hz without DSC, or there may be a DP2.1 issue with macOS, whatever.

However, since 5K2K at 165 Hz was previously confirmed to work with M3 Pro using DP 1.4 with DSC, what if you try disabling DP 2.1 in your 45GX950A's settings, fall back to DP 1.4 mode, and test again?

<< - DisplayPort over USB-C

- `LinkRateDescription = "8.1 Gbps (HBR3)"`. >>

HBR3 is the fastest s speed over USB-3, at 8.64 G bits/sec, just short of top USB 3 speed of 10 G bits/sec.

to run a Full 5K display at 10 bits color at 60 Hz without resorting to Display Stream Compression requires UHBR10 at 38.69 G bits/sec, just short of Top Full Thunderbolt-3/4 speed.

to run a 5K2K display at 10 bits color at up to 99 Hz without resorting to display Stream Compression requires UHBR10 at 38.69 G bits/sec, just short of Top Full Thunderbolt-3/4 speed.

it appears that forcing this data stream into a USB 3 port is what is limiting your resolutions.

--------

the best high performance adapter to DisplayPort that really can attain ThunderBolt-3/4 AND 5 speeds is this new CableMatters adapter:

USB-C to DisplayPort 2.1 Adapter

Product ID:  201386. Price:   $35.00 

https://www.cablematters.com/search.aspx?PageSize=20&PageNum=1&SearchTerm=201386

There are two regressions here. The first is the one you mentioned: it affects starting from the M4 series. For example, the M4 Pro cannot achieve `3840x1620 HiDPI 165Hz` with HDR enabled, but it *can* achieve `3840x1620 HiDPI 165Hz` without HDR at 10-bit color, full RGB. whereas the M3 Pro supports this with HDR without any problem. This applies to all ports and connectivity methods, including native HDMI, USB-C/Thunderbolt, and USB-C/Thunderbolt to Dock/DP.

The M5 series’ native HDMI port shows the same behavior as the M4 series. BUTTTTT the M5 series has a separate regression on the USB-C/Thunderbolt ports, where you get even fewer options no matter what kind of port/adapter/dock you try.

I ran into this exact problem last year when I bought a Mac Studio M4 Max to replace my old 2017 Intel iMac.

Incredibly, my old iMac can drive higher resolutions on my LG 40WP95C-W Ultrawide than this brand-new Mac Studio. It’s hard to believe that a machine nearly 10 years older handles display scaling better than one of Apple's most powerful current computers.

So far, the only workaround has been using the BetterDisplay app to create a virtual screen and associate it with the physical LG monitor. While it works, it’s far from an ideal native solution.

I’m honestly very disappointed. We are investing a lot of money into 'pro' hardware, only to find these limitations. It’s even more frustrating to hear that users with M5 chips are still facing the same issues. 

<< I'm using the supplied USB-C able and even tried a TB5 cable with no fix. >>

'Supplied' by whom?

Cables shipped in the box by most display-makers are guaranteed to have the correct connectors on the ends. Beyond that, they are often "lowest bidder" cables and are often inadequate for driving high-end displays at high resolutions.

Cables required for DisplayPort at near 4K and beyond should be high spec cables and are limited to ONE meter maximum at these data rates.

An ordinary Thunderbolt-5 cable, if operating at Thunderbolt speeds, is limited to 0.5 meters max for brand-X cables. There are a few highly engineered cables available that can run a little bit longer. Beyond that, you generally need an ACTVE Thunderbolt-5 cable, which starts at about US$100.

andreeinprogress wrote:

cedric1088 wrote:

Hello again andree. I don't know if you'll ever see this, but if you do, could you please give it a try?

I may have a theory about your 45GX950A being capped at 100 Hz.

I checked the manual of the 45GX950A. It only supports 5K2K at 165 Hz, 100 Hz and 60 Hz. There's no 120 Hz option. And we know that at least 120 Hz is required to enable 3860x1680 HiDPI layout.

Now, the question is why 165 Hz doesn't show up with the latest M5 Pro using TB5. The only difference between M5 Pro and M3 Pro is that the M5 Pro's TB5 connector supports DisplayPort 2.1, whereas TB4 on M3 Pro only supports DP 1.4 with DSC.

One possible explanation is that the downgraded DP 2.1 54 Gbps bandwidth version (commonly used by LG) may not be sufficient for 5K2K at 165 Hz without DSC, or there may be a DP2.1 issue with macOS, whatever.

However, since 5K2K at 165 Hz was previously confirmed to work with M3 Pro using DP 1.4 with DSC, what if you try disabling DP 2.1 in your 45GX950A's settings, fall back to DP 1.4 mode, and test again?

• Hey, thanks! Yes I'm reading all messages here (and AFAIK someone from Apple should be too).

Thanks for the suggestion but I already tried that, without success. (really tried pretty much every combination on phone with support).

on TB5, with every cable I tried, 2.1 option is not even available, so it's 1.4

• on direct DP with a proper cable both 2.1 and 1.4 are available. the only differences in setting it to 1.4 are that it enables HDR (only on low resolutions), but also caps at 100Hz

Thank you very much for the update.

I strongly believe there is a serious regression with how the M5 Pro handles DSC under DP 1.4 mode.

I don't know if DSC is required to run 5K2K at 100Hz, but it's definitely required for 165Hz. I see two possibilities.

1. If DSC is required for 100Hz, M5 Pro's DSC limit might have been lowered from 165Hz to 100-120Hz range.
2. If DSC is not required for 100Hz, M5 Pro's DSC might not work at all for whatever reason.

Hopefully it works with 120Hz, but 45GX950A doesn't support 120Hz, we need someone with Dell U4025QW to do a test.

It's tied to M5 Pro, not the port, because some users have reported that it works on the M4 Pro, which has the same Thunderbolt 5 port with DP 2.1.

The remaining question is whether it works on the base M5, which doesn't support DP 2.1 at all. If its DSC feature is broken, its usability is gravely compromised.

I agree with many posters here that these M5 Macs, and possibly some M4 Macs as well, seem to have issues that go well beyond the limited input speeds on certain displays or wrong cables. They have issues with not being able to set up fast enough connections. Most of this looks to me like a problem in the Mac, and I expect there will eventually be a software solution.

Be sure you use the Apple Product fFeedback pages or contact telephone support (Both references above) and let them know, so that the stack of complaints gets tall enough to tip over and they fix this mess.

Well.. This worked! Amazing, thanks!

Im now using my M5 Pro with the LG 40WP95C screen on 3840x1620!

At first it did show a message; "Out of range", and half the screen was flickering. So i changed the Hz from 120 to 60 (as the monitor is a 72Hz max) and now it's all good!

Obviously had to purchase BetterDisplay Pro to test it out. Glad it's working, and hopefully Apple will come with a software-update for this in the near future.

that LG 45GX950A-B appears to be 5120 by 2160 (5K2K display capable of 10 bits/color and refresh rates from 48 to 165 Hz.

connectivity includes:

2x HDMI 2.1

2x DisplayPort 2.1 (UHBR 13.5 w Display Stream Compression (DSC)

USB-C 3.1. top speed would be 10 G bits/sec, called out as a data transmission port

Those specs and others available do not say that display is capable of direct Thunderbolt connection.

¿Are you using an adapter or adapter/cable? which one?

andreeinprogress wrote:

There is obviously something different happening with this particular chip. You can even see from the screenshots that the M1Pro and the M3Pro have 5 resolutions available, while the M5Pro does not.

The "like 3840x1620@165Hz" scaling mode that you want implies an internal drawing canvas that is as wide as an 8K display, and 75% as tall as an 8K display. Maybe driving this monitor in "like 3840x1620@60Hz" mode uses up the same sort of display generation resources that driving an 8K@60 Hz monitor, in non-Retina mode, would.

Have you tried connecting the M5 MBP to the monitor with a HDMI v2.1 cable, and lowering refresh rate to 60Hz?

Also, have you tried telling Displays Settings to show resolutions as a list? Maybe you will see some extra Retina scaling modes pop up.

In this example, the three choices highlighted in green are not choices in icon view, even though they are available in list view. (Here, the Mac is a M1 Max Mac Studio and the monitor is a UHD 4K (3840x2160 pixel) monitor.). (The less useful choices following 1920x1080 (Default) don't show up in icon view, either.)

<< I have tried with: a TB5 cable (which is compatible), a USB4 cable (which is compatible), a USB3.1 cable. All the same. >>

and I have said, "None of those direct connections should be working AT ALL"

according ti the manufacturers specs and third-party reference sites, that display does not have a Thunderbolt input port, and connection to the USB-C port might not work at all.

If we pretend for a moment that the display's USB-C port actually will accept data, it will be very limited in highest resolutions and refresh can be displayed.

¿Is that similar to what you are complaining about?

¿Is the link you posted for the EXACT model number you are running? LG has a half dozen or more all called UltraWide.

¿is you display actually this 40WP95C-W ?