Kernel Panic With 4k 240 Hz External Monitor

This bug still exists on macOS 15.6.1. I am super disappointed. I pay premium prices for Apple products that are always marketed as “Pro” and “for professionals,” yet they still can’t support 4K 240Hz properly. This has been around for about a year with no fix. Every macOS update I try to enable 240Hz again, and every time it lets me down.

Same. 2-3 crashes per day. Have a Samsung LS49CG932SNXZA with a proper USB certified cable.

panic(cpu 0 caller 0xfffffe0027d03644): DCPEXT1 PANIC - apt firmware: dual_pipe.c:180 sync_pipe_end_of_config() --  - iomfb_mailbox(70)
apt firmware: dual_pipe.c:180 sync_pipe_end_of_config() -- 
RTKit: RTKit-2784.140.9.release - Client: AppleDCP-811.120.13~3320-t602xdcp.RELEASE
!UUID: a1000010-2140-1ed5-a178-80d201401ed5
ASLR slide: 0x000000000005c000
Time: 0x000003d7c050d606

Faulting task  70 Call Stack: 0x000000000007b884 0x000000000007b24c 0x000000000007b058 0x0000000000073cb8 0x00000000001d8298 0x0000000000212060 0x0000000000211dac 0x000000000020f294 0x000000000007bcb8 0x00000000000768b4 000000000000000000
RTKit Task List:
   name                    | pri     | stack use | status     | resource | warning
 0 rtk_background          | 007     |   832/2048  | SEMWAIT    | 0x958600 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

 1 rtk_ep_work             | 057     |   904/2048  | SEMWAIT    | 0x954be0 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

 2 log_tx                  | 007     |   608/2048  | SEMWAIT    | 0x9416f0 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

 3 log_flush               | 015     |   928/4096  | SEMWAIT    | 0x940a90 | 
      0x0000000000075d38 0x0000000000076d6c 0x0000000000082404 0x00000000000768b4

 4 tracekit_work           | 007     |   592/4096  | SEMWAIT    | 0x93e5c0 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

 5 power                   | 000     |  1568/65536 | RUNNABLE   | 0x7356a8 | 
      0x0000000000075d38 0x000000000007aa24 0x000000000007a744 0x00000000000768b4

 6 Terminator              | 015     |   416/2048  | SEMWAIT    | 0x92cc90 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

 7 main                    | 015     |  8656/40960 | SEMWAIT    | 0x928170 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x000000000006a384 0x000000000006c60c

 8 dcpexpert               | 015     |   240/16368 | SEMWAIT    | 0xffffffff0c011f40 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

 9 rtkitpmgr               | 015     |   240/16368 | SEMWAIT    | 0xffffffff0c031f40 | 
      0x0000000000075d38 0x0000000000076d6c 0x000000000007bc4c 0x00000000000768b4

(snip)

I'm also getting this issue on a ROG PG32UCDM:

panic(cpu 1 caller 0xfffffe0017b13410): DCPEXT0 PANIC - apt firmware: dual_pipe.c:180 sync_pipe_end_of_config() --  - iomfb_mailbox(50)
apt firmware: dual_pipe.c:180 sync_pipe_end_of_config() -- 
RTKit: RTKit-2758.1.1.release - Client: AppleDCP-811.1.1~291-t602xdcp.RELEASE
!UUID: a1000010-2140-1ed5-a178-80d201401ed5
ASLR slide: 0x0000000000367000
Time: 0x00000786450ad51f

It seems to occur most frequently when I'm using Discord, which I believe is an app rendering via Electron? I've had some issues with apps like this on Windows too where they behave weird. I wonder is that any clue to the issue?

Anyway, +1 to this needing a fix.

Unfortunately I also got a kernel panic while using 26.1, so indeed nothing has been fixed.

There probably is nothing here for Apple to fix. More than likely you need to use a different higher grade cable.

This is incorrect. The kernel panic happens with Apple's own Thunderbolt 4 cable as well, as already reported in this thread. What even higher grade cable are you referring to?

Users here are seeing this as something Apple accidentally broke, when in fact it is really Apple trying to make things work better for the newer higher resolution HD displays...

This is also incorrect. There is absolutely no excuse for a kernel panic, regardless of the cable used. This is a serious issue in the code, which can and should be fixed. Connection with a poor quality cable may be unstable, may flicker, may disconnect every other second, etc. but the kernel may not crash like this but has to fail gracefully. It's pointless to come up with excuses why Apple shouldn't fix this because it's the user's fault. It's not the user's fault. And I know my stuff too.

Infilak wrote:

Yes, it's unfortunate to not be able to use the highest refresh rates on our 240 Hz monitors. I hope Apple fixes this sometime soon.

MacOS 15.1 has been released.

Any changes?

Thanks! The ASUS PG32UCDP has a completely different LG WOLED panel, so it seems the issue isn't limited to Samsung QD-OLED panels.

Exactly same issue here. 2 panics already. Mac Studio M4 Max with Dell U4025QW. And this display goes only to 120Hz.

a VPN is a great way to get you to be "present" on in institutional network, or other single point on the globe that is better than where you are actually located.

Many vendors push their VPN software as a way to improve security. Nothing could be further from the truth. A VPN sends all your data over EXACTLY the same wires to a point of the Internet where it is concentrated for easy data harvesting. VPN vendors have already been fined for doing this, regardless of their promises to the contrary.

But you do not have A VPN installed. you have at least parts of FOUR:

 VPNs:

    [Loaded] HSSHydraNetworkExtension - /Applications/Hotspot Shield.app

    [Loaded] HSSWireGuardNetworkExtension - /Applications/Hotspot Shield.app

    [Loaded] HydraTunnelProvider - /Applications/Hotspot Shield.app

    [Loaded] WireguardTunnelProvider - /Applications/Hotspot Shield.app

¿What is the date of your most recent backup, and by what method?

if VPN vendors stuck with doing VPN, using them they would be a modestly bad idea. But most VPN vendors also scan your files for Viruses, often intervening in your Internet activity to break into encrypted connections to be FIRST to scan your files, and leave it less secure to completely broken. VPN for any purpose by institutional network presence is just a bad idea.

pixelwave wrote:

As I wrote in my post.. that is the version I am on. So no …

The original poster is Infilak.

This is not your discussion thread, you are hijacking it.

You have no posted your etrecheck report, and all manner of things might be happening to your system alone.

Thunderbolt output is definitely not limited to 60Hz. At 6K the maximum is indeed 60Hz but that is because 6K has much higher bandwidth requirements. These vague specs neither confirm nor deny that higher refresh rates are supported at lower resolutions but in practice macOS does offer up to 240Hz at 4K, so it is actually supported.