1.4. Bus

A bus is a set of electrical circuits used to transport binary data that has been converted to electrical signals, enabling communication among all of the components of a server.

Many types of buses work together in a server to provide high performance with minimal bottlenecks. The basic types of buses found in a server include the following:

• Processor bus Is internal to the processor

• Backside bus Connects the processor or processors to the on-board cache memory

• Frontside bus Connects the processor to the system controller chipset

• Memory bus Connects the main memory to the memory controller

• Local I/O bus Connects high-speed internal and external I/O devices to the I/O controller hub

• Expansion I/O bus Connects I/O ports, expansion I/O controllers, and expansion slots to the I/O controller hub

Each server bus type is made up of two electrical lines, which are also known as buses.

The first type is the address or control bus. This bus identifies the desired location within a target device where data might reside. It also carries control signals that indicate the purpose of the data transfer, such as whether a device is supposed to read or write the data.

The second type is the data bus. Data moves between any two devices over the data bus. The data can be instructions for the microprocessor or information the microprocessor is transmitting. This information can pass to or from the memory or I/O subsystem.