Memory Address Register

Memory-Address Register

The Memory-Address Register is a CPU register that either:

• Holds the memory address from which data can be fetched to the CPU registers, or

• Holds the memory address two which data will be sent and stored via the system bus.

The MAR is used to access data and instructions from memory during the execution phase of instruction. The MAR holds the memory location of data that needs to be accessed.

When reading, data addressed by the MAR is fed into the MDR and then used by the CPU. When writing to memory, the CPU writes data from MDR to the memory location pointed to by the MAR.

MAR, which is found inside of the CPU, goes to RAM or cache.

Memory Buffer Register/Memory Data Register (MDR)

is the register in the CPU that stores the data being transferred to and from the immediate access storage.

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