I also encountered a similar bug.
Test setup:
Core boards: CM4, CM5
IO boards: official CM4 IO board, official CM5 IO board
Display: HDMI monitor (powered independently with its own 5V supply)
Observation:
CM4 + official IO board → boots normally with HDMI connected
CM5 + official IO board → fails to boot if HDMI is connected (seems like HDMI is back-powering the board and blocking startup)
CM4 core + CM5 IO board → boots normally
CM5 core + CM4 IO board → still fails to boot
Conclusion:
Since CM4 always works under the same conditions, but CM5 always fails, this strongly suggests the issue is with the CM5 core board itself, not the IO boards or the monitor.
Question:
Is this a known issue with CM5?
Could it be related to HDMI power/back-powering or missing protection on CM5?
Any recommended workaround?
Test setup:
Core boards: CM4, CM5
IO boards: official CM4 IO board, official CM5 IO board
Display: HDMI monitor (powered independently with its own 5V supply)
Observation:
CM4 + official IO board → boots normally with HDMI connected
CM5 + official IO board → fails to boot if HDMI is connected (seems like HDMI is back-powering the board and blocking startup)
CM4 core + CM5 IO board → boots normally
CM5 core + CM4 IO board → still fails to boot
Conclusion:
Since CM4 always works under the same conditions, but CM5 always fails, this strongly suggests the issue is with the CM5 core board itself, not the IO boards or the monitor.
Question:
Is this a known issue with CM5?
Could it be related to HDMI power/back-powering or missing protection on CM5?
Any recommended workaround?
Statistics: Posted by Amarantos — Tue Aug 26, 2025 8:18 am