2.2 Computer hardware architecture

< Free Open Study >

A computer system is comprised of the five building blocks previously described, as well as additional peripheral support devices, which aid in data movement and processing. These basic building blocks are used to form the general processing, control, storage, and input and output units that make up modern computer systems. Devices typically are organized in a manner that supports the application processing for which the computer system is intended-for example, if massive amounts of data need to be stored, then additional peripheral storage devices such as disks or tape units are required, along with their required controllers or data channels.

A computer system's architecture is constructed using basic building blocks, such as CPUs, memories, disks, I/O, and other devices as needed.

To better describe the variations within architectures we will discuss some details briefly-for example, the arithmetic logic unit (ALU) and the control unit are merged together into a central processing unit or CPU. The CPU controls the flow of instructions and data in the computer system. Memories can be broken down into hierarchies based on nearness to the CPU and speed of access-for example, cache memory is small, extremely fast memory used for instructions and data actively executing and being used by the CPU and usually resides on the same board or chip as the CPU. The primary memory is slower, but it is also cheaper and contains more memory locations. It is used to store data and instructions that will be used during the execution of applications presently running on the CPU-for example, if you boot up your word processing program on your personal computer, the operating system will attempt to place the entire word processing program in primary memory. If there is insufficient space, the operating system will partition the program into segments and pull them in as needed.

The portion of the program that cannot be stored in memory is maintained on a secondary storage device, typically a disk drive. This device has a much greater storage capacity than the primary memory, typically costs much less per unit of storage, and has data access times that are much slower than the primary memory. A more recent external storage device is the CD-ROM drive. This device, in its read-only mode (ROM), allows users only to extract information from the drive. In the more recent read/ write variety the device can be used somewhat like the traditional tape drive. An additional secondary storage device is the tape drive unit. A tape drive is a simple storage device that can store massive amounts of data-again, at less cost than the disk units but at a reduced access speed. Other components of a computer system are input and output units. These are used to extract data from the computer and provide these data to external devices or to input data from the external device. The external devices could be end-user terminals, sensors, information network ports, video, voice, or other computers.

In the following sections we will examine each of the components of a computer system in more detail, as we examine how these devices can be interconnected to support data processing applications.

< Free Open Study >