Microprocessor Design/Memory Unit

Microprocessors rely on memory for storing the instructions and the data used by software programs. The memory unit is responsible for communicating with the system memory.

Actions of the Memory Unit
All von Neumann CPUs store their instructions in memory.

In a Harvard architecture, the data memory unit and the instruction memory unit are two different units. However, in a Princeton architecture the two memory units are combined into a single module. Most modern PC computer systems are Princeton, not Harvard, so the memory unit must handle all instruction and data transactions. This can serve as a bottleneck in the design.

Timing Issues
The memory unit is typically one of the slowest components of a microcontroller, because the external interface with RAM is typically much slower than the speed of the processor.