The original 'ps' got the data by reading kernel memory directly (/dev/kmem or /dev/mem), and I'm old enough to remember systems doing that. I don't think ther

The original 'ps' got the data by reading kernel memory directly (/dev/kmem or /dev/mem), and I'm old enough to remember systems doing that. I don't think there were any Unix-derivatives that used system calls? Minix is closest, in that you could query the 'mm' task using RPCs which are sort of system calls.