Why does the system monitor show less RAM than is installed in the system? - TUXEDO Computers

Those using Linux – for example, in TUXEDO OS – may notice that the system monitor or the command free -h in the terminal displays less memory than is actually installed in the device. This effect can particularly occur in systems with an integrated graphics unit (iGPU). But what is the reason for this?

Memory Usage by the Integrated GPU

Unlike dedicated graphics cards that have their own video memory (VRAM), an iGPU shares the regular system memory (RAM). A portion of the RAM is reserved by the integrated graphics and is not available to the operating system or other applications. The amount of reserved memory („Shared Memory“) can vary but is usually adjustable in the BIOS/UEFI.

Example: iGPU Usage in TUXEDO OS

On a laptop with 32 GB of RAM and an iGPU, it may happen that the system monitor only shows about 27.2 GB as available. This is because, for example, 4 GB of RAM is allocated to the graphics unit (the odd values arise from the conversion of gigabytes to gibibytes).

To check the exact memory allocation, you can use the following command in the terminal. Here you will find an entry for the memory allocation of the iGPU:

sudo dmesg | grep VRAM
(out)    3.713720 amdgpu 0000:03:00.0: amdgpu: VRAM: 4096M 0x000 - 0x000 (4096M used)
(out)    3.713734 drm Detected VRAM RAM=4096M, BAR=4096M
(out)    3.713858 drm amdgpu: 4096M of VRAM memory ready

Adjusting the Reserved RAM Amount

The reserved RAM amount for the iGPU can be set in the BIOS/UEFI for devices with AMD CPU/iGPU, for example. There is an option like iGPU Configuration or UMA Framebuffer size, through which you can increase or decrease the reserved memory. On many TUXEDO devices, the BIOS automatically manages the memory allocation.

Conclusion

If less RAM is displayed under TUXEDO OS or another Linux distribution than is actually installed, it may be due to the integrated graphics unit. This uses a portion of the RAM as video memory. Those who wish to adjust the reserved memory can usually do so via the BIOS/UEFI. A balanced setting helps to find a good balance between system performance and graphics performance.