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M4 Pro Mac Mini Persistent DCP Kernel Panics with LG OLED (TB5 / DSC / 480Hz)

Hello everyone,


I am looking to see if anyone else with a Mac mini (M4 Pro) and a high-refresh OLED (specifically the LG 27GX790B-B) has found a permanent workaround for recurring Display Coprocessor (DCP) kernel panics.


The Issue: 

My system consistently panics during power state transitions (Wake-from-sleep and entering Sleep). I have moved through three distinct failure modes documented in my logs:


  1. Mailbox Timeout: DCPEXT1 PANIC - apt firmware: video_mode_main_init.c:195 main_init() -- - iomfb_mailbox(72)
  2. Memory Abort: A DATA ABORT (Null Pointer) at far=000000000000000000 when manually locked at 60Hz.
  3. Power Down Failure: DCPEXT2 PANIC - power_down_M3: auto_mode_change failed with 0x8000000f when using BetterDisplay to stabilize the wake cycle.


System Setup:

  • Host: Mac mini M4 Pro (macOS 15.3 Sequoia)
  • Primary Display: LG 27GX790B-B OLED connected via certified Thunderbolt 5 cable.
  • Secondary Display: Gigabyte M27Q via HDMI.
  • Peripherals: 80Gbps NVMe SSD, Motu M2 Audio Interface.


Troubleshooting Performed:

  • Implemented staged sleep timers (displaysleep 2, sleep 15) to ensure the DCP settles before the kernel powers down.
  • Reduced refresh rate from 480Hz to 144Hz and 60Hz (Panics persist, error type just shifts).
  • Configured BetterDisplay to force-disconnect displays on sleep.
  • Moved the secondary monitor to HDMI to reduce Thunderbolt bus saturation.


It appears the M4 Pro’s AppleDCP driver has a fundamental timing incompatibility with the DSC (Display Stream Compression) handshake on high-end OLED TCONs. Curiously, this issue never occurred with dual M27Q monitors at 170Hz (uncompressed).


Has anyone found a specific refresh rate, EDID override, or "Magic" cable configuration that stops the M4 Pro from tripping over its own display engine?

Mac mini, macOS 26.3

Posted on Mar 12, 2026 9:46 AM

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User profile for user: Bostonhack
Bostonhack Author
User level: Level 1
10 points

Posted on Apr 9, 2026 3:15 PM

Hi DKsean,


Just an update: I decided to RMA the LG 27GX790B-B. It was a bit of a bummer since I got it for $200 off on an intro promo, which felt like a steal for a new release. Interestingly, my unit had an April 2025 manufacture date, whereas the one Rtings reviewed was from December 2025. It makes me wonder if there were some early production quirks with those launch units.


I ended up swapping it for the new ASUS PG32UCDM3. It’s a different format, but the bandwidth demands are actually even higher. I’ve been running the ASUS via HDMI (saving the DP for my gaming PC) and have had zero crashes over two weeks of sustained use. I even tested it via Thunderbolt 5—rock solid.


When comparing the LG 27GX790B-B and the ASUS PG32UCDM3 over HDMI 2.1, the bandwidth bottleneck shifts from refresh rate to pixel density depending on the panel. The LG, running at 1440p and 480Hz, demands a massive raw data rate of approximately 58.5 Gbps for a 10-bit HDR signal, which significantly exceeds the 48 Gbps maximum uncompressed capacity of HDMI 2.1. Consequently, the LG must utilize Display Stream Compression (DSC) to hit its flagship 480Hz refresh rate. In contrast, the ASUS PG32UCDM3 operates at a native 4K resolution at 240Hz. Even though its refresh rate is lower than the LG's, the jump to 4K means it is pushing roughly 8.3 million pixels per frame; at 240Hz with 10-bit color, the ASUS requires a staggering 71.6 Gbps of raw bandwidth. Because this is nearly 50% beyond the limit of the HDMI 2.1 spec, the ASUS also relies heavily on DSC to maintain its 4K/240Hz output. Ultimately, both monitors require DSC to function at their peak specs, but for different reasons: the LG is bottlenecked by its extreme frequency, while the ASUS is pushed over the edge by its high resolution.


Regarding Grant’s suggestion that the M4 MacBook Pro might have a hardware fault: I was skeptical of that, as the only way to truly find the root cause was to see if the problem was replicable. Since the Mac handles the Gigabyte M27Q and the new ASUS flawlessly at high bandwidths, AND that my PC has no issues with the LG, it really points toward a specific handshake or software issue between Apple and that LG panel, rather than a hardware failure on the Mac's part.

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User profile for user: Bostonhack
Bostonhack Author
User level: Level 1
10 points

Mar 12, 2026 12:56 PM in response to Grant Bennet-Alder

Thanks for your help, I can see this isn't going to be a simple fix. What bothers me is that all this started the moment I plugged in the new monitor. I could (but haven't tried yet) put back my old monitor and see what happens. I'm betting it stops crashing. (I have 21 days left to return this monitor. Could the monitor have a hardware problem??)


At first, I thought it just couldn't handle the 480Hz and focused on that. I couldn't even get the Mac to start when I first plugged it in as the monitor defaults to 480Hz, and won't let you change the refresh until AFTER you have it running! That initial testing may have fried some circuit which is not presenting as a hardware problem. If that's the case, then when I plug the old monitor back in, it should still crash. (I had the old monitors running at 170Hz, no problem. So I think that's worth at least a test.)


I also have an older Mac M1 laptop that I could test this with, but I wouldn't want to cause any damage if that's what this was.


I've been using Google Gemini to help me, and Gemini is convinced it's a software issue. But it sometimes gets confused and it may be hallucinations ;)


But I'm leaning towards it being a software problem too, which is why I don't think bringing it in for service is going to solve my issue. Thanks for all the info and debugging steps. I do use Time Machine to back up to an external SSD, and I'm on the latest version. I may try some of your suggestions like running a clean user account. I have been posting the panic reports, though you get no feedback...

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M4 Pro Mac Mini Persistent DCP Kernel Panics with LG OLED (TB5 / DSC / 480Hz)

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