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~ ~ Welcome students, I look forward to working with you this semester, check this site frequently for updates and assignments. ~ JON ~
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~ IST ~ Chapter 9
Computer switches Switches: Devices inside the computer that can be flipped between these two states: 1 or 0, on or off Nonmechanical devices in computers that open and close circuits Types of electrical switches: Vacuum tubes Transistors: Semiconductors Integrated circuits Binary number system Computers work in binary language Consists of two numbers: 0 and 1 Everything a computer does is broken down into a series of 0s and 1s Inside the CPU The CPU Machine Cycle Fetch The programs binary code is fetched from its temporary location in RAM and moved to the CPU Decode The programs binary code is decoded into commands that the CPU understands. Execute The ALU performs the calculations. Store The results are stored in the registers System Clock Located on the motherboard Controls the CPUs processing cycles Clock cycle Pulse or tick Clock speed Number of pulses per second Measured in hertz (Hz) The CPU is the brains of the computer Different types of CPUs Intel and AMD chips: Used in most Windows-based PCs Apple systems use different CPU design Differentiating CPUs Processing power Clock speed and cache The Algorithmic Logic Unit Part of the CPU designed to perform mathematical operations (addition, subtraction, multiplication, division, etc.) Also performs logical OR, AND, and NOT operations Is fed data from the CPU registers Word size: Number of bits a computer can work with at a time
The Control Unit Manages the switches inside the CPU Is programmed by CPU designers to remember the sequence of processing stages for that CPU Moves each switch to its correct setting (on or off) Then performs the work of that stage
American Standard Code for Information Interchange (ASCII) 8 bits = 1 byte = alphanumeric character or symbol 256 different combinations Unicode 16 bits equal 1 byte 65,000 different combinations, used for all languages Cache Memory Small amount of memory located on the CPU chip or near it Stores recent or frequently used instructions and data Used for quick access by the CPU Different levels of cache Types of RAM Volatile: When you turn off your computer, the data is erased Several kinds of RAM exist Each type of RAM has a different design Some types work at much faster speeds Some transfer data more quickly Static RAM (SRAM) Does not lose its electrical charge Faster than DRAM More expensive than DRAM Used only in locations like cache memory Dynamic RAM (DRAM) Cheapest and most basic type of RAM Loses its electrical charge Needs to be refreshed Many types of DRAM SDRAM: Synchronous DRAM DDR SDRAM: Double data rate SDRAM Computer buses Electrical pathway used to move data between components Local bus: Connects the CPU with the memory Expansion bus: Connects the CPU with peripheral devices Bus clock speed Rate of speed data moves from one location to another Measured in MHz (millions of clock cycles per second) Bus width The number of bits of data moved on a bus at any one time Measured in bits 16 bits 32 bit Types of Buses ISA and EISA Found on older computers Connects mouse, modem, and sound card PCI Faster than ISA and EISA Found on modern computers Connects network, modem, and sound cards AGP Used for three-dimensional graphics Connects the graphics card and memory Creating faster CPUs Pipelining: The CPU processes more than one instruction at a time Dual processing Two CPUs on the same system Each processor shares the workload Parallel processing Network of computers Each computer works on a portion of the problem simultaneously Moores Law Number of transistors on a CPU will double every 18 months First chip had 29,000 transistors Pentium chip 169,000,000 transistors Moores Law has been accurate for more than 40 years Law has remained accurate into the 21st century
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