Difficulty setting GPU memory split

Troubleshooting
1

Creating a bug report/issue

I have searched the existing open and closed issues

Required Information

  • DietPi version | 10.1.2
  • Distro version | trixie 0
  • Kernel version | 6.12.75
  • Architecture | arm64
  • SBC model | RPi 5 Model B (8G)
  • Power supply used | 27W RPi PSU
  • SD card used | amazonbasics 128G U3 microSD

Additional Information (if applicable)

Steps to reproduce

  1. Install DietPi
  2. Set gpu memory split in dietpi-config to 96
  3. Check GPU memory: vcgencmd get_mem gpu

Expected behaviour

  • vcgencmd get_mem gpu returns gpu=96M
  • vcgencmd get_mem arm returns arm=8096M

Actual behaviour

  • vcgencmd get_mem gpu returns gpu=8M
  • vcgencmd get_mem arm returns arm=1016M

Extra details

  • This post might be related.
  • Afterwards, I tried setting gpu_mem manually in /boot/firmware/config.txt, but vcgencmd still gives the same values. This does update what’s said in dietpi-confighowever.

Snippet from /boot/firmware/config.txt:

#-------GPU memory splits-------
gpu_mem_256=256
gpu_mem_512=256
gpu_mem_1024=256
gpu_mem=256

I don’t know if vcgencmd is reporting incorrectly, or if my GPU memory split isn’t actually being adjusted. I don’t know how to check either. The whole reason I’m trying to adjust this in the first place is because I can’t manage to watch videos of any resolution. I’ve already ruled out CPU throttling, browser, internet, and microSD performance.

Any help would be appreciated. Thanks.

2

VideoCore VII allocates the memory dynamically, so vcgencmd show just nonsense.
https://forums.raspberrypi.com/viewtopic.php?t=366298