Logical & Physical Address

1. Logical & PhysicalAddress Nihal Güngör

2. LogicalAddress • In simplest terms, an address generated by the CPU is known as a logical address. • Logical addresses are also referred to as virtual addresses. • The logical address space is the set of logical addresses generated by a program. • From the perspective of a program that is running, an item seems to be located in the address provided by the logical address. • *That program usesthevirtualmemory at the time.

3. PhysicalAddress • Physical address(also called the real addresses) is the actual memory address which denotes a memory area in your storage device. • Physical address is the address seen by the memory unit and it allows accessing a particular memory cell in the main memory by the data bus.

4. Application programs that are running on the computer do not see the physical addresses. • They always work using the logical addresses. • Logical addresses need to be mapped to physical addresses before they are used and this mapping is handled using a hardware device called the Memory Management Unit (MMU). • There are several mapping schemes used by the MMU.

5. Physical address or the real address is the address seen by the memory unit and it allows the data bus to access a particular memory cell in the main memory. • Logical addresses generated by the CPU when executing a program are mapped in to physical address using the MMU. • All the logical addresses need to be mapped in to physical addresses before they can be used.

6. A logical cache, also known as a virtual cache, stores datausing virtual addresses. • The processor accesses the cache directly, without goingthrough the MMU. • A physical cache stores data using main memory physicaladdresses.