Philips 34" 346P1CRH not Supporting Full Resolution at 100Hz

Today, I installed Windows 10 using Boot Camp on my MacBook to see, whether the problem persists using the same hardware but a different OS and graphics driver. After installing the current driver from the AMD website, I connected the monitor over USB-C and it instantly showed me the full resolution at 100Hz.

So it is definitely not some hardware defect on my computer. As the monitor is working correctly with basically every other device I try, we can also rule out a defect on the monitors side. From my understanding it looks like the problem can only be on the software side and with all the tests I've already tried it looks like the problem can only be within the graphics driver.

Right now, I've also tried it with a different Macbook (13" MacBook Pro 2016), which which it worked totally fine. This Model does to have a discrete graphics card, whereas my 16" MacBook has a Radeon 5500M 4GB in addition to the Intel UHD graphics. I think it has something to do with the discrete graphics card not supporting my monitor correctly or with the switching between the two cards. Unfortunately there is no way, to force the MacBook to use only the integrated graphics card. Maybe there is a problem with the driver?

Thanks for pointing that out. I know, that in the Heading it is only advertised as 4k@60Hz, but if you look in the description, you can see, that it also supports for example 2K@165Hz. Most of the cables advertise only the highest possible resolution at 60Hz, but in the end what matters is, what version of USB the cable supports, which in the case of my cable is USB 3.2 Gen 2x2 which should support data transfers up to 20 Gbit/s. Furthermore also the monitor as well as the Computer have to support the same USB-generation. From what I know, my monitor only supports USB 3.2 Gen 2, which supports a transfer rate of 10 Gbit/s.

If you calculate the bandwidth needed for displaying 3440 x 1440 @ 100Hz you need about 12.76 Gbit/s (assuming there is no compression involved and using full RGB color format) of data which is roughly the same as with 3840 x 2160 (4K/UHD) @ 60Hz which is at 12.54 Gbit/s.

What's also to note is, that the monitor works at the advertised 3440 x 1440 @ 100Hz with all Windows-Devices I've testet so far (including my own MacBook under BootCamp) and it also works with two other MacBooks with a different graphics card. So it is definitely not a problem of the cable.

I contacted the Apple Support, but unfortunately, they also couldn't help me with the problem.

Today I had the opportunity to try the monitor with a different MacBook Pro 16" (2019), with which it works perfectly fine at the full resolution and refresh rate. In contrast to my model, it has the 5300M graphics card built in.

It's strange, that only my MacBook causes the problem, even if I already tried it with a fresh install of macOS, NVRAM reset, PRAM reset, etc.. And at the same time every other monitor works correctly with my MacBook.

This was one of the first things I changed in my monitor OSD. If I set it back to USB 3.2 the maximum resolution I can set in the macOS settings is 2560 x 1440 @ 60 Hz.

@tspavan: Until now unfortunately no. The maximum I get with my MacBook is still 3440 x 1440 @ 60Hz. As soon as I find a solution I will write it here.

@Grant: I also have a 49" Monitor with a resolution of 5120 x 1440 pixels and a maximum refresh rate of 60Hz, with which I don't have any problems using it at full resolution. This also worked with macOS Catalina, before Big Sur even got published, using only a single USB C cable. According to the technical specifications of my model, it should support up to two monitors at 6K resolution or up to four 4K monitors. Therefore, a single monitor with less than 4K resolution at a 100Hz, shouldn't be a problem.

Interestingly my MacBook works perfectly fine with the predecessor of my monitor (Philips 346B1C), which a friend of mine has, at 3440 x 1440 @ 100Hz. This also proves, that my MacBook is indeed capable of displaying such a resolution in combination with 100Hz.

I know, that both operating systems have a different approach to displays, but as I said, it also works with two other Macs over the same cable. One MacBook Pro from 2016 with only the integrated Intel UHD graphics and another MacBook Pro from 2019, which is basically the same MacBook, that I have, with the only difference being, that mine has the AMD 5500M graphics card and the other one I tested only has the 5300M.