No, the RAM is on a separate chip. The RPi0 and RPi1 have the RAM chip sat directly on top of the SoC (so it looks like one chip unless you look closely) but for all other RPis they are on different parts of the PCB. The SoC does have some cache memory on-chip for the CPUs but that is nothing to do with the amount of RAM.
Well...maybe. Given that the system issues a sync command periodically, those disk caches will get cleared. Plus, not all programs write very much, so not much caching may be needed.
The dirty pages get flushed. Others remain.W. H. Heydt wrote: ↑Tue Oct 22, 2019 8:50 pmWell...maybe. Given that the system issues a sync command periodically, those disk caches will get cleared.
Disk reads are cached as well of course (read a file or run a large program for the first time, and its slow because it must be read from the disk. Read the same file, or run the same program some time later, and it will be fast because its come from the cache).
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[email protected]:~ $ df Filesystem Size Used Avail Use% Mounted on /dev/root 59G 9.9G 47G 18% / devtmpfs 1.8G 0 1.8G 0% /dev tmpfs 1.9G 0 1.9G 0% /dev/shm tmpfs 1.9G 8.5M 1.9G 1% /run tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup tmpfs 1.9G 768K 1.9G 1% /tmp tmpfs 16M 600K 16M 4% /var/log /dev/mmcblk0p1 253M 53M 200M 21% /boot tmpfs 386M 0 386M 0% /run/user/1000 [email protected]:~ $