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CH04_SystemMotherboardPorts

# CH04_SystemMotherboardPorts - Chapter 4 System Unit CPU...

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Chapter 4: System Unit: CPU, Motherboard, and Ports Goal The objective of this and the next chapter is to make the reader familiar with the most important hardware, to explain the basic principles of how hardware works, and to teach basic methods to compare quality and performance of different hardware options. Comparison of hardware performance requires measurement and quantification. Thus, the chapter starts with an introduction to quantities and units used in computing. Computing Units and Quantities There are four main types of quantities that are used to rate and compare performance of computer and computer components: amount of data, rate of events or speed of cycles, rates of data transfer, and amount of time it takes to complete a given operation or process. Q UANTITY OF D ATA The bit , derived from the phrase ―binary digit,‖ is the smallest amount of information in the digital world. A bit can have only two states: This can be thought of as on or off, yes or no, true or false, north or south, 1 or 0. This way of representing information as collections of bits is perfect for the nature of transistors, which are used in computers as on/off switches. The fact that each switch can have only two states without intermediate states gives digital computers their robustness, but also some of their deepest limitations. For the everyday use of personal computers, the limitations are not relevant. A byte is a group of 8 bits. They are grouped because together they can code 2 8 = 256 different characters and symbols. In fact, the ASCII (pronounced as-key) is simply a table that indicates what number or byte corresponds to each character of the alphabet, punctuation, digits, etc. Bytes were already used in the early computers, and the term ―byte‖ was first used by Dr. Werner Bucholz when he worked at the IBM corporation in 1956. Units of capacity and speed Amount of data bit Kb, Mb, Gb byte KB, MB, GB Speed for cycles (CPU and buses) Hertz = 1 cycle per second KHz, MHz, GHz Speed for data transfer (data/time) bps (bits per second) Kbps, Mbps, Gbps Time to access memory or storage Millisecond Microsecond

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CPU, Motherboard, RAM, Ports, etc 4-2 Inside a computer, all data are represented digitally, and stored in circuits that can be either on or off. Binary numbers allow these circuits to represent numbers. Each circuit represents one binary digit, or bit. Eight bits make up one byte. One bit can represent two values; two bits represent 4 values; 3 bits represent 8 values, and so on. The total number of values is calculated as 2 to the N power, where N is the number of bits. Special codes including ASCII, EBCDIC, and Unicode allow numbers to be interpreted as letters or special characters. Unicode uses 16 bits to encode characters, which gives it enough room to store more than 65,000 different symbols, allowing computers to handle the characters of most languages. B
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CH04_SystemMotherboardPorts - Chapter 4 System Unit CPU...

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