The method or scheme of managing memory depends upon its hardware design. In larger operating systems, many copies of the same application can be running. Memory management deals with the ways or methods through which memory in a computer system is managed. The Memory Management Unit (MMU) The Memory Management Unit (MMU) performs translations. Contiguous virtual memory space is created out of a pool of equal size blocks of virtual memory for running the application. The memory management unit often assigns an application the memory address that best fits its need. Instead of the user receiving an error message that there is not enough memory, the MMU automatically instructs the system to build enough virtual memory to execute the application. The CPU accesses this information held in the memory cache, which helps speed up the processing time. Another way to use an MMU is to implement “thread protected mode” or “lightweight process model”. One of the main challenges for memory management unit is to sense when data is no longer needed and can be discarded. During its operation a CPU generates a sequence of addresses, along with a a read/write signal, indicating the memory location or peripheral device register that it wishes to access. Each process behaves as if it has free use of the entire CPU. • Memory Management Unit (MMU) – Hardware unit that translates a virtual address to a physical address – Each memory reference is passed through the MMU – Translate a virtual address to a physical address • Translaon Lookaside Buﬀer (TLB) This provides much of the protection of process model, with a lower overhead on each context switch. This frees up memory for use on other processes. The same technology is conceptually simple, but may be incredibly complex in its implementation. This permits a separation of “virtual addresses” [used by the software on the CPU] and “physical addresses” [used by the memory and peripheral hardware. The most common use of an MMU is to facilitate deployment of a “process model” operating system, like Linux. When the physical memory, or RAM, runs out of memory space, the computer automatically uses virtual memory from the hard disk to run the requested program. In computing, an input–output memory management unit (IOMMU) is a memory management unit (MMU) that connects a direct-memory-access–capable (DMA-capable) I/O bus to the main memory. Memory caches are used to hold copies of certain data from the main memory. When the physical memory, or RAM, runs out of memory space, the computer automatically uses virtual memory from the hard disk to run the requested program. Like a traditional MMU, which translates CPU-visible virtual addresses to physical addresses, the IOMMU maps device-visible virtual addresses (also called device addresses or I/O addresses in this context) to physical addresses. In most RTOSes, an MMU has not been traditionally used and all memory is visible at all times. I am thinking about a Memory Management Unit [MMU] …. When the operation is completed, the memory is recycled for use elsewhere. The memory management unit is usually integrated into the central processing unit. Obvious question: why is this remapping desirable, useful or necessary? © 2020 Siemens Digital Industries Software. If the MMU is set up appropriately, parts of the mapping may be switched off as each task is scheduled. A memory management unit (MMU) is a computer hardware component that handles all memory and caching operations associated with the processor. This feature is a major key to making this process work effectively and efficiently because the system is not required to create one chunk of virtual memory to handle the program requirements. Inefficient memory management presents a major issue when it comes to optimal performance of computer systems. Although the memory management unit can be a separate chip component, it is usually integrated into the central processing unit (CPU). The automated paging process allows the operating system to utilize storage space scattered on the hard disk. RAM is the physical storage compartment that is located on the hard disk. The memory management unit allocates memory from the operating system to various applications. Thus, no remapping of addresses occurs, but only the memory for the current task, and relevant parts of the OS, is visible at any one time. Also, the memory management unit can distribute memory resources to programs on an as needed basis. An MMU’s job is to take the address asserted by the CPU and translate [map] it to an alternative address. The virtual address area, which is located within the central processing unit, is comprised of a range of addresses that are divided into pages. It is curious to consider some technology that, to many engineers, is rather mysterious, whilst, to others, is indispensable.