I have a Raspberry Pi 4 (8GB) loaded with the latest arm64 testing image. Everything has been stable so far. When looking in Cockpit, I noticed that the system is reporting 2.8GB of total system memory. Running ‘free -m’ via ssh reports the same.
I’ve confirmed that the image loaded is 64-bit. Is there something I need to do to make the full 8GB (or 7.XGB) available?
You may not be able to use more than 3 GB of RAM, even if you have a 4 GB or 8 GB model, unless your OS is patched for DMA access (which, in Linux, requires kernel 5.8 or later). This is the result of a hardware bug in the Broadcom CPU that powers the Rapsberry Pi 4.
To use more than 3 GB, and provided your OS has been patched for such use, you need to go to Device Manager → Raspberry Pi Configuration → Advanced Settings in the UEFI settings.