Microprocessor Design/Memory Unit

From Wikibooks, open books for an open world
< Microprocessor Design
Jump to: navigation, search

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.

Memory Unit[edit]

Memory Unit.svg

Actions of the Memory Unit[edit]

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[edit]

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.