Chapter 2 (Topic 2): Inside the System Unit

CHAPTER 2: HARDWARE

Topic 2: Inside the System Unit

The system unit is the main case of a computer. In general, the system unit contains a CPU, several types of memory, interfaces to connect external peripheral devices (such as printers), and other components all interconnected through sets of wires called buses on the motherboard.

Inside the System Unit

Motherboard:

The main circuit board inside the system unit is called the motherboard. The motherboard has a variety of chips, boards, and connectors attached to it. Typically, external devices (such as monitors, keyboards, mouse, and printers) connect to the motherboard by plugging into a port. A port is a special connector exposed through the exterior of the system unit case.

The Power Supply and Drive Bays:

The power supply unit gives the supply of current to the mother board and the other attached devices in the main system unit. Most of computers (such as desktop computers) also contain drive bays (rectangular metal racks) inside the system unit into which storage devices (a hard drive and DVD drive) can be inserted. Storage devices inside the system unit are connected via a cable to the motherboard. Many desktop computers come with empty drive bays so users can add additional storage devices as needed.

Central Processing Unit (CPU):

The computer’s brain or heart, the CPU is a computer’s main chip. The CPU is also called the microprocessor. Most personal computers today use CPUs manufactured by Intel or Advanced Micro Devices (AMD). In earlier the names were actually based on numbers like 8088. The next few name in the series the 286, the 386, and the 486, were actually just shortened names for 80286, 80386, and 80486. Then, what would have been the 586 was dubbed the Pentium. After that, the names became moderately strange: Pentium and Pentium Pro. Finally, the names returned to Pentium 2, Pentium 3, and Pentium 4. Intel makes most CPUs. In fact, Intel is the company that came up with the name Pentium. However, AMD Technology is other well-known CPU manufacturer. Their CPUs are less expensive and use a different naming system (such as the AMD Athlon and the AMD Duron). Intel actually makes a less expensive version of the Pentium as well, which it calls the Celeron. The Celeron does what the Pentium does, but not as quickly. The CPU is really nothing more than an incredibly fast and powerful calculator. 

AMD Duron Processor: It has less built-in memory and is designed for people on a budget.

AMD Athon Processor: The Athlon processor is equivalent to Pentium processors but only it’s less expensive.

Intel Celeron Processor: Intel’s Celeron CPU is an inexpensive processor designed for people on budget. Celeron processors are very similar to Pentium processors, but they have less built-in memory. 

Intel Pentium I, II, III and 4 Processors: Launched in 1999, Pentium 4 CPUs are still found in some new computers.

Multi-core CPU: A CPU that contains the processing components or core of more than one processor in a single CPU.

Dual-core CPU: A CPU that contains two separate processing cores.

Quad-core CPU: A CPU that contains four separate processing cores.

While CPUs just a few years ago used 32-bit words (referred to as 32-bit processors), most CPUs today are 64-bit processors (that is, they are capable of using 64-bit words, in addition to 32-bit words). Usually, a larger word size allows for faster processing and the use of more RAM, provided the software being used is written to take advantage of 64-bit processing. Computer with a 64-bit processor running the 64-bit version of the Windows operating system can use more RAM and has a higher performance than the same computer running the regular 32-bit version of Windows.

Cache Memory:

Cache memory is a special group of very fast memory circuitry located on to the CPU. Cache memory is used to speed up processing by storing the data and instructions that may be needed next by the CPU.

Bus Width, Bus Speed, and Bandwidth

A bus is an electronic path over which data can travel. There are buses inside the CPU, as well as on the motherboard. You can picture a bus as a highway with several lanes; each wire in the bus acts as a separate lane, transmitting one bit at a time. The number of bits being transmitted at one time is dependent on the bus width. Just as a wider highway allows more cars to travel at one time, a wider bus allows more data to be transferred at one time.

Bus Width