how to determine the size of physical memory on the PCB?

hi there

i'm wondering about the question as presented in the topic, how can the system get the size of physical memory, by some CPU instruction set?

or the size information is set by some hardware configuration?

Thanks a lot

Perhaps I am not understanding the question fully. If you just want to see how much physical RAM there is, you can do something like:

cat /proc/meminfo

i mean, a system like linux is always independent of the hardware it's running on, right?

whether on a hardware with 2M memory or one with 128M memory, it can be the same linux system.

so, how can the system determine the memory size of the hardware?

or in another way, if i write a small system like uC-OS, and i don't want it that before install the system i have to configure the code and tell the system how much memory is there in case it runs overflow. so is there anyway to checkout how much memory is there in a view of software, instead of checking the chip on the PCB?

as for the file /proc/meminfo, that's the 'conclusion' of 'system determination'