The Central Processing Unit (CPU) interacts with primary memory, also referred to as main memory or RAM, via the system bus. This bus is responsible for transmitting data, addresses, and control signals, thereby enabling the CPU and memory to work in concert to execute programs and process information.

The system bus comprises three primary components: the data bus, the address bus, and the control bus.

1. Data Bus: This bus is responsible for carrying the actual data being processed. The width of the data bus, which refers to the number of wires it contains, directly impacts the volume of data that can be transmitted simultaneously.

2. Address Bus: The address bus carries the addresses of specific memory locations. These addresses indicate where data is stored in memory or from where it should be retrieved.

3. Control Bus: The control bus transmits signals that coordinate and manage the operations of the computer, such as initiating read or write commands.

When the CPU needs to read from or write to primary memory, it first sends a signal through the control bus to indicate whether a read or write operation is required. Next, the CPU transmits the address of the targeted memory location via the address bus. If the operation is a read, the data stored at that location is sent back to the CPU over the data bus. Conversely, if the operation is a write, the CPU sends the data to be written to the memory location via the data bus.

This communication process is overseen by the memory controller, a digital circuit responsible for managing the data flow to and from the computer’s memory. The memory controller may exist as a separate chip or be integrated directly into the CPU.

In summary, the interaction between the CPU and primary memory is facilitated by a sophisticated system of buses and controllers. This infrastructure is crucial for the effective transport of data, addresses, and control signals, which are essential for program execution and data processing within the computer system.