Computer Architecture

13.3 Data Buses

13.3.1 Internal And External Buses

Internal buses connect the various registers and components of the CPU.

External buses connect the CPU to the main memory and the periherals.

13.3.2 Single And Shared Buses

Single Bus

A single bus is a dedicated bus that connects two units unidirectionally.

With multiple units the number of single bsues required grows rapidly.

Advantages

• Permits simultaneous data transmission

Disadvantages

• Costly in terms of wires
• Requires a high number of pins on the units

Shared Bus

Often a shared bus system is preferred.

Advantages

• Extra units can be easily added

Disadvantages

• Does not permit simultaneous transmission of data

Shared buses are usually bi-directional

13.3.3 Interfacing With Peripherals

Input/Output devices and data storage devices communicate with the CPU via external buses.

The peripherals require an interface unit.

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