What is the purpose of an mmu (memory management unit)?

[MadRat]

I was reading another post when the idea of a mmu (memory management unit) was mentioned. Can someone explain this in brevity?

 

[SCSIRAID]

The MMU allows the flat memory model that the program being run thinks it has, to be mapped into real memory which may be fragmented in pieces throughout real memory or even paged out to the HDD. It translates the address generated by the program instruction stream into a physical memory address or a page miss which says the referenced memory block is actually on the HDD. Descriptors set up by the OS indicate what physical memory is allocated to the program.

 

[CTho9305]

good answer... basically, it lets you pretend that all your memory is one contiguous block, so programs dont have to worry about handling where stuff is, and whether it is presently in memory or swapped to disk/elsewhere

 

[BFG10K]

And it also lets a program think that it's the only one open even though multiple programs might be open.