Understanding Computers, Ch.31 Chapter 3 The System Unit: Processing and Memory

Understanding Computers, Ch.32 Learning Objectives Understand how data and programs are represented to a computer and be able to identify a few of the coding systems used to accomplish this. Explain the functions of the hardware components commonly found inside the system unit, such as the CPU, memory, buses, and expansion cards. Describe how new peripheral devices or other hardware can be added to a PC.

Understanding Computers, Ch.33 Learning Objectives, Cont’d. Understand how the computer system’s CPU and memory components process program instructions and data. Name and evaluate several strategies that can be used today for speeding up the operations of computers. List some technologies that may be used in the future PCs.

Understanding Computers, Ch.34 Overview This chapter covers: How computers represent data and programs How the CPU, memory, and other components are arranged inside the system unit How the CPU works Strategies to speed up a computer and create faster computers

Understanding Computers, Ch.35 Data and Program Representation Computers today are mostly digital computers— devices that can only understand two states. The two states of a digital computer are typically represented by 0s and 1s; that is, in binary form. Computers do all processing and communications in binary form, so natural-language input and output are translated to and from binary by the computer.

Understanding Computers, Ch.37 The Binary Numbering System We normally use the decimal numbering system, which uses 10 symbols (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9). Computers use the binary numbering system, which represents all numbers using just two symbols (0 and 1).

Understanding Computers, Ch.38

9 Coding Systems for Text-Based Data ASCII and EBCDIC Fixed-length codes that can represent any single character of data as a string of eight bits. Unicode A longer (32 bits per character is common) code that can be used to represent text-based data in virtually any written language.

Understanding Computers, Ch.310 Coding Systems for Other Types of Data Graphics data —often stored as a bitmap which the color to be displayed at each pixel stored in binary form. Audio data —waveform audio is common; MP3 compression makes audio files much smaller. Video data —requires a great deal of storage space, but can be compressed.

Understanding Computers, Ch.311 Machine Language Machine language is the binary-based code used to represent program instructions. The basic set of machine language instructions that a CPU can understand is that CPU’s instruction set. Most programmers rely on language translators to translate their programs into machine language for them.

Understanding Computers, Ch.312 Inside the System Unit The system unit of a PC is the case that houses processing hardware and other hardware. All of the hardware contained within the system unit is connected to the system board or motherboard.

Understanding Computers, Ch.314 CPU The CPU (central processing unit) does the vast majority of processing for a computer. CPUs contains a variety of circuitry and components and are connected to the motherboard. Also called the processor or microprocessor.

Understanding Computers, Ch.315 CPU, Cont’d. Processing speed (clock speed) is measured in megahertz (MHz) or gigahertz (GHz) and measures the number of clock ticks per second. A computer word is a group of bits or bytes that a CPU can manipulate at one time. Other factors that affect the speed of the computer include the amount of RAM and cache memory, bus width, and bus speed.

Understanding Computers, Ch.316 Memory: RAM RAM (random access memory) is the computer’s main memory and is used to temporarily storage programs and data with which it is working. RAM is volatile (erased when the power to the PC goes off). RAM comes in a variety of types, speeds, and size. Types of RAM include: DRAM SRAM SDRAM DDR SDRAM RDRAM DDR-II SDRAM

Understanding Computers, Ch.317 Memory: Other Types Cache memory—fast memory chips located on or close to the CPU chip (L1, L2, and L3). Registers—high speed memory built into the CPU. ROM (read-only memory)—non-volatile chips inside which data or programs are stored. Flash memory—non-volatile memory that can be erased and reused. Used both within the PC and for portable storage media (e.g digital cameras).

Understanding Computers, Ch.318 Buses Buses are electronic paths that data travels around on a computer system. Internal buses move data around within the CPU. Expansion buses establish links with peripheral devices. ISA, PCI, AGP, USB, FireWire.

Understanding Computers, Ch.320 Expansion Slots and Cards Expansion for desktop PCs. Expansion cards can be inserted into expansion slots on the motherboard. Some external devices can be plugged into existing USB or FireWire ports without adding another expansion card. PC cards—used with notebook PCs. Expansion for handhelds and mobile devices—can have proprietary, PC card, or SDIO slot.

Understanding Computers, Ch.321 Ports Connectors to which devices can be attached. Common ports: Serial Parallel SCSI USB FireWire Network Keyboard Mouse Monitor Modem MIDI IrDA Game

Understanding Computers, Ch.323 How the CPU Works The CPU is a collection of electronic circuits and components. Impulses from an input device passes through RAM and enters the CPU via a system bus. Within the CPU the impulses move through the circuits and components to create new impulses. Eventually, a set of electronic impulses leaves the CPU for an output device.

Understanding Computers, Ch.324 Typical CPU Components Arithmetic/logic unit (ALU) Control unit Registers Prefetch unit Decode unit Internal cache Bus interface unit

Understanding Computers, Ch.326 The System Clock and the Machine Cycle The system clock synchronizes the computer’s operations. The machine cycle is the series of operations involved in the execution of a single, machine-level instruction. Fetch Decode Execute Store

Understanding Computers, Ch.328 Making Computers Faster Now and in the Future Speeding up your system today. Add more memory. Perform system maintenance. Buy a larger or second hard drive. Upgrade your Internet connection. Upgrade your video card. Upgrade your CPU.

Understanding Computers, Ch.329 Summary Data and program representation Inside the system unit How the CPU works Making computers faster now and in the future