Chapter 9: A Closer Look at System Hardware

Chapter 9: A Closer Look at System Hardware CS10001 Computer Literacy Chapter 9: A Closer Look at System Hardware 1

Topics Discussed Digital Data and Switches Manual Electrical Digital Data Representation Decimal to Binary (Numbers) Characters and Symbols Other (Negative, Fractional, Hexadecimal) CPU Digital Processing Machine Cycle In-Depth Machine Cycle Stages Chapter 9: A Closer Look at System Hardware 2

Digital Data Recall that bits are the alphabet of the binary language. They represent the status of off (0) or on (1). Bits may be thought of as language devices that control the states of off or on. They are considered to be binary switches. Chapter 9: A Closer Look at System Hardware 3

Digital Data Electrical switches are devices inside the computer with the capability of representing the states of the binary language, 0 or 1. So, computers are nothing more than big devices of electrical switches? How is that accomplished? Chapter 9: A Closer Look at System Hardware 4

Examples of Switches Vacuum tubes allowed or blocked the flow of electrical current in early computers (1940s). Big Bulky Unreliable Unsafe Vacuum tube Chapter 9: A Closer Look at System Hardware 5

Examples of Switches Transistors incorporated silicon semiconductors to allow or block the electrical flow of digital information. Smaller Cheaper Cooler Still big Transistors Chapter 9: A Closer Look at System Hardware 6

Examples of Switches Integrated circuits are microprocessors, or chips, embedded with a CPU. Contains millions of transistors in a very small space (1970s). Smallest Cheapest Fastest Integrated circuit Chapter 9: A Closer Look at System Hardware 7

Digital Data Representation Recall that the binary number system is the language of computers. It is used by the computer to represent all data, instructions and programs. Because it is a number system, it is an organized plan for number representation. It consists of two digits: 0 and 1. Chapter 9: A Closer Look at System Hardware 8

Converting Decimal Numbers to Binary Technique #1 1. Find the largest base 2 number in the decimal number. 2. Set that placeholder to on or 1. 3. Subtract that number from the original decimal number to get a remainder. 4. Perform steps 1-3 on the remainder until the binary number is determined. Chapter 9: A Closer Look at System Hardware 9

Converting Decimal Numbers to Binary Technique #2 1. Divide the decimal number by 2. 2. Calculate the remainder as 0 or 1. 3. Perform steps 1-2 until all divisions are exhausted. 4. The binary number is determined by writing the remainder digits from the bottom to the top. Chapter 9: A Closer Look at System Hardware 10

Storing Letters and Symbols in Binary EBCDIC (Extended Binary Coded Decimal Interchange Code) Provided the first means of consistent representation of letters and characters that the computer could understand. Used in early mainframes. Chapter 9: A Closer Look at System Hardware 11

Storing Letters and Symbols in Binary ASCII (American Standard Code for Information Interchange) Used to represent letters or characters in one byte. Included 26 uppercase letters and 26 lowercase letters, punctuation symbols and special characters. Allowed for 2 8 or 256 combinations. Chapter 9: A Closer Look at System Hardware 12

Storing Letters and Symbols in Binary Unicode Expanded ASCII and allowed a representation of all characters and all symbols for all languages (historic and modern). Utilized 16 bits for the representation of one byte. Allowed for 2 16 or approximately 65,000 combinations. Chapter 9: A Closer Look at System Hardware 13

Other Binary Representations Negative numbers Uses a sign bit CPU notified by program Fractional numbers Utilize a 32-bit system Representations standardized by IEEE (Institute of Electrical and Electronics Engineers) Chapter 9: A Closer Look at System Hardware 14

Other Binary Representations Hexadecimal numbers Uses an alphabet of 16 digits, 0-9 and A-F. Easier representations for humans because binary strings are too long and cumbersome. Where else was the hexadecimal number system discussed? This will likely be seen on our class project. Chapter 9: A Closer Look at System Hardware 15

The CPU and Digital Processing Recall that the CPU is: The brains of the computer. Fits on a microprocessor chip. Is located on the motherboard with memory. Executes all the instructions (userdefined or operating system). Is part of the computer system s platform. Chapter 9: A Closer Look at System Hardware 16

The CPU and Digital Processing How are CPUs different? By processing power (number of transistors). By clock speed (its work pace). By amount of immediate access memory (cache). By hyperthreading (processing two separate instruction sets--one before the other finishes or both simultaneously). Chapter 9: A Closer Look at System Hardware 17

In Depth: The CPU Machine Cycle Recall that the machine cycle is the pace at which instructions and programs are processed by the CPU. Measured in Hz (Hertz) and clock speed, as determined by the system clock. It has four steps: fetch, decode, execute and store. Chapter 9: A Closer Look at System Hardware 18

In Depth: The CPU Machine Cycle The system clock is built into the motherboard and controls the stages of the machine cycle. Its clock cycle beats steadily and sets the processing pace. The clock speed is the pace at which machine cycles are occurring. Chapter 9: A Closer Look at System Hardware 19

In Depth: The CPU Machine Cycle The CPU s control unit manages the switches inside the CPU so that it can remember the proper stage of the machine cycle (preprogrammed). With each beat of the system clock, switches are set for that stage. The work associated with that stage is performed. Chapter 9: A Closer Look at System Hardware 20

In Depth: Machine Cycle Stages Fetch Stage Gathers the necessary binary code for the instruction or program from RAM. Moves the instruction from RAM to the CPU registers which are special storage areas on the CPU. The instruction remains in the registers until executed. Chapter 9: A Closer Look at System Hardware 21

In Depth: Machine Cycle Stages Fetch Stage cont d: Using cache memory Level 1 is on the CPU. Level 2 is on the CPU but farther away. Chapter 9: A Closer Look at System Hardware 22

In Depth: Machine Cycle Stages Decode Stage Translates the instruction into something the CPU understands. Uses specific instruction sets for the translation. Signals the registers (via the control unit) about which data to send to the ALU. Chapter 9: A Closer Look at System Hardware 23

In Depth: Machine Cycle Stages Execute Stage Data is sent to the ALU from the registers, based on word size. The ALU performs the calculations on the data. Arithmetic: Add, Subtract, Multiply, Divide Comparison: <, >, =, not equal Logical: AND, OR, NOT Chapter 9: A Closer Look at System Hardware 24

In Depth: Machine Cycle Stages Store Stage Result from the ALU is stored in the registers. Register for storage is noted in the instruction. The cycle begins again with the next instruction to be processed. Chapter 9: A Closer Look at System Hardware 25

Other Topics Discussed Other RAM Dynamic RAM Static RAM The Bus Local bus Expansion bus Making Computers Faster Pipelining New instruction sets Multiple processing Parallel processing Chapter 9: A Closer Look at System Hardware 26

RAM: More Temporary Storage Recall that RAM: Is located on the motherboard in memory modules (memory cards). Holds all the data and instructions needed by the CPU and OS. Has an access time measured in nanoseconds. Measured in MB or GB. Chapter 9: A Closer Look at System Hardware 27

RAM: More Temporary Storage DRAM (Dynamic RAM) Cheap and basic Access time = 60ns Uses transistors, capacitors and refresh signals for individual bits. Chapter 9: A Closer Look at System Hardware 28

RAM: More Temporary Storage DRAM (Dynamic RAM) cont d. Hierarchy SDRAM (synchronous DRAM) DDR SDRAM (double data rate SDRAM) DDR2 SDRAM Chapter 9: A Closer Look at System Hardware 29

RAM: More Temporary Storage SRAM (Static RAM) Faster than DRAM More expensive than DRAM Uses more transistors for bits, but no capacitors or refresh rates Commonly used for the CPU cache Chapter 9: A Closer Look at System Hardware 30

RAM: More Temporary Storage What else about RAM memory modules? DIMMs (dual inline memory modules) Pentium processors, 64-bit bus SIMMs (single inline memory modules) Pre-Pentium processors, 64-bit bus was emulated in matched 32-bit buses Chapter 9: A Closer Look at System Hardware 31

Bus: CPU Data Highway A bus is an electrical wire located within the system circuitry. Considered to be a data highway This highway is traveled by data (bits) and links the various computer components. Chapter 9: A Closer Look at System Hardware 32

Bus: CPU Data Highway Two bus types: Local bus On the motherboard CPU to main memory data transfer Expansion bus From expansion cards to motherboard Seen in video and audio Chapter 9: A Closer Look at System Hardware 33

Bus: CPU Data Highway Bus Speed More Data at a Time? Bus clock speed is the data transfer rate from one location to another (MHz). Bus width determines the number of bits traveling at a time (wider is better). Bus clock speed X bus width = Data transfer rate of the bus. Chapter 9: A Closer Look at System Hardware 34

Bus: CPU Data Highway Bus Speed More Speed with the Data? The bus width determines the word size to the CPU, or the number of bits manipulated at a time. What happens if the CPU can manipulate more bits than the bus delivers? Bus width limitations affect the CPU s processing performance. Chapter 9: A Closer Look at System Hardware 35

Bus: CPU Data Highway Expansion buses ISA and EISA connected mouse, modem, sound card. PCI direct CPU connection for networks and sound. AGP for graphics transfer so the PCI is not clogged. See page 424 for architecture details. Chapter 9: A Closer Look at System Hardware 36

Making Faster Computers Advanced CPU Designs Pipelining New instruction sets Multiple processing Parallel processing Chapter 9: A Closer Look at System Hardware 37

Making Faster Computers Pipelining is a technique used to boost CPU performance. CPU works on more than one instruction at a time. More instructions processed in a clock cycle. More efficient CPU processing. Chapter 9: A Closer Look at System Hardware 38

Making Faster Computers Nonpipeling vs. Pipelining Instruction 1 Nonpipelined CPU Fetch Decode Execute Store Instruction 2 Fetch Decode Execute Store Pipelined CPU Instruction 1 Fetch Decode Execute Store Instruction 2 Fetch Decode Execute Store Instruction 3 Fetch Decode Execute Store Instruction 4 Fetch Decode Execute Store Chapter 9: A Closer Look at System Hardware 39

Making Faster Computers New instruction sets The basic instruction set is the collection of commands executable by a specific CPU. New commands to accommodate video, audio and image processing are inserted in the basic instruction set. New instruction sets are the result. Chapter 9: A Closer Look at System Hardware 40

Making Faster Computers Multiple processing Dual-processor Two physical CPU chips installed Used on high-end servers or mainframes Dual-core processing Uses hyperthreading Runs multiple stages of the machine cycle simultaneously Appears as if two CPU chips are present Chapter 9: A Closer Look at System Hardware 41

Making Faster Computers Parallel processing Designed to solve one complex problem. Large network of computers. Each computer works on part of the problem. Tasks are completed simultaneously. Chapter 9: A Closer Look at System Hardware 42