4.3 The CPU Bus

The bus is the mechanism by which the CPU communicates with memory and devices. A bus is, at a minimum, a collection of wires but it also defines a protocol by which the CPU, memory, and devices communicate. One of the major roles of the bus is to provide an interface to memory. (Of course, I/O devices also connect to the bus.) Based on understanding of the bus, we study the characteristics of memory components in this section, focusing on DMA. We will also look at how buses are used in computer systems.

4.3.1 Bus Organization and Protocol

A bus is a common connection between components in a system. As shown in Figure 4.3, the CPU, memory, and I/O devices are all connected to the bus. The signals that make up the bus provide ...

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