Everything You ever Wanted To know about Virtual Memory

[Murphy's Law]

>(iii) All processes have the same adress space but cannot write on sections
>of memory that belong to other processes. (One of the proposed designs for
>MOOSE, some research OSes for 64 bit machines)
>[Ie. process X might "own" addresses 1000-2000 and process Y owns 4000-5000.
>Process X can still REFER to address 4500 -- if memory protection allows it
>to. This reference will be to the memory used by process Y]

I don't like the idea of processes being able to read all the data from
other processes..  


That would entail a few things that could cause problems -- 
	A)  A tendency to rely on fixed addresses
	B)  insecurity on a possible multiuser implementation *shrug*
	C)  programs having to keep track of their own addresses.
 
I think it might be a lot simpler to have the process that needs to access 
data from another task make a call to the object, passing it a way of writing (or some way of communicating between the processes) and passing a copy of the
data.  There are fast instructions, eg, MOVSW / MOVSD on the 386, and there are
comparable on the 680x0, so it wouldn't be that hard..  and objects can control what they want to share!
 
Just my fraction of a penny.