Computer Architecture

Section A Digital Electronics CHAPTER 5 Computer Architecture Page 206

Section A Digital Electronics Chapter 5 SectionPREVIEW Section D Section A You will be able to: • Identify the components that are on the main circuit board - the motherboard -of a microcomputer Page 207

Section A Digital Electronics Chapter 5 Section A • Computer architecture refers to the design and construction of a computer system. • based on power source • based on how computer physically represents, processes, moves, and stores data • Modern computers are powered by electricity and use electric signals and circuits to represent, process, and move data. Page 207

Inside the System Unit What does the inside of a computer look like? Chapter 5 Section A CD-ROM drive Power Supply Floppy disk drive Hard disk drive Circuit boards Wires and ribbon cables Page 207

Integrated Circuits Why isn’t the system unit filled with a lot of wires? Chapter 5 Section A • Most electronic components inside a computer are integrated circuits - thin slices of silicon crystal packed with microscopic circuit elements • wires • transistors • capacitors • resistors Page 209

Integrated Circuits Why isn’t the system unit filled with a lot of wires? Chapter 5 Section A • Inside a computer, you are likely to find several kinds of chip packages, including DIP, DIMM, PGA, and SEC. Example of DIPs Page 209

The Motherboard How do the chips fit together to make a computer? Chapter 5 Section A • Chips are housed on a circuit board called a motherboard. • contains processor chip • computer memory chips • chips that handle basic input/output • contains expansion slots for peripheral devices • Some chips are soldered (permanent), some are removable (can be upgraded) Page 210

The Motherboard How do the chips fit together to make a computer? Chapter 5 Section A Support chips Random access memory chips ROM chips Microprocessor chip Circuitry Expansion cards Page 210

Digital Data Representation If a computer is just a bunch of electrical circuits, how can it manipulate data? Chapter 5 Section A • Most of today’s computers are digitaldevices • work with distinct numbers or digits • An analogdevice operates on continuously varying data The pulse of electricity down a circuit could represent 1 bit Page 211

Data Representation Codes Do all digital computers use the same code to represent data? Chapter 5 Section A • Computers represent data using the binary number system and several other codes designed for computer data. • Binary number system (base 2) • has only two digits: 1 and 0 • converted into “ons” and “offs” • number 2 cannot be used • Numericdata - numbers that represent quantities Page 212

Data Representation Codes Do all digital computers use the same code to represent data? Chapter 5 Section A • Character data is composed of letters, symbols, and numerals that will not be used in arithmetic operations. • name, address, etc. • Digital computers represent character data using ASCII (American Standard Code for Information Interchange) and EBCDIC. • IBM-brand mainframe computers often use EBCDIC (Extended Binary-Coded Decimal Interchange Code). Page 212

Data Representation Codes Do all digital computers use the same code to represent data? Chapter 5 Section A An example of data codes Page 213

Data Transport What happens to the data in a computer? Chapter 5 Section A • Data travels from one location to another on an electronic circuit called a data bus. • Databus - series of circuits that connect various electrical components on the motherboard • contains data lines and address lines • Datalines - carry the signals that represent data • Addresslines - carry signals that specify where computer can find data to process Page 214

Section B Memory CHAPTER 5 Computer Architecture Page 215

Section B Memory Chapter 5 SectionPREVIEW Section D Section B You will be able to: • Explain how RAM, virtual memory, ROM, and CMOS differ Page 215

Section B Memory Chapter 5 Section B There are four major types of memory, each characterized by the data it contains and the technology it uses to hold the data. Page 215

Random Access Memory How does RAM work? Chapter 5 Section B • RAM (random access memory) - an area of the computer that holds data before and after it is processed • as you type, characters are held in RAM • Capacitors are microscopic electronic parts that hold the electronic signals for the code that represents data. • charged capacitor = ON • discharged capacitor = OFF • each bank of capacitors holds eight bits Page 215

Random Access Memory How does RAM work? Chapter 5 Section B Each RAM location has an address and holds one byte of data by using eight capacitors to represent the eight bits in a byte. Page 215

Random Access Memory How does RAM work? Chapter 5 • A RAMaddress on each bank helps the computer locate the data in that bank. • RAM is a reusable computing source. • RAM is volatile: requires power to hold data. Page 215

RAM Functions Why is RAM so important? Chapter 5 Section B Section B • RAM • holds data waiting to be processed • holds instructions that will process the data • holds processed data before it is stored elsewhere • holds operating system instructions Page 216

RAM Capacity, Speed, and Configuration How much RAM does my computer need? Chapter 5 Section B Section B • Storage is measured in RAM • Today’s computers have between 64 and 256 megabytes of RAM • Amount of RAM depends on software you use • You can purchase additional RAM • Today’s RAM has access speeds as fast as 8 nanoseconds, one billionth of a second • RAM is configured as a series of DIPS soldered onto a circuit board called a DIMM Page 216

Virtual Memory What if I run out of RAM? Chapter 5 Section B Section B • A computer can use disk storage to simulate RAM. This is called virtual memory. • not as fast as RAM Page 217

Read-Only Memory If a computer has RAM, why does it need ROM? Chapter 5 Section B • ROM (read-only memory) is one or more chips containing instructions that help a computer prepare to process tasks. • Since RAM is empty when a computer is turned on, ROM BIOS is used. • ROM BIOS (basic input/output system) is a set of instructions that tells computer how to access the disk drives and peripheral devices. Page 218

CMOS Memory If the boot instructions are permanent, can I change any hardware on my system? Chapter 5 Section B • A computer needs a semi-permanent way of keeping boot data, such as the number of hard disk sectors and cylinders. • CMOSmemory - holds data but requires very little power to retain its contents. • can run by a battery on the motherboard • housed within the same chip carrier as ROM BIOS • Some computers have plug and play feature for updating CMOS. Page 218

Section C Central Processing Unit CHAPTER 5 Computer Architecture Page 220

Section C Central Processing Unit Chapter 5 SectionPREVIEW Section D Section C You will be able to: • Explain how the CPU performs instructions contained in a computer program • List the factors that affect CPU performance Page 220

Section C Central Processing Unit Chapter 5 Section C The central processing unit is the circuitry in a computer that executes instructions to process data. Page 220

Central Processing Unit Architecture What does the CPU look like? Chapter 5 Section C • In 1945, the size of a CPU was measured in feet; today, they are measured in mils (0.001 inch) The ENIAC built in 1944 was two feet wide and eight feet high. Page 220

Central Processing Unit Architecture What does the CPU look like? Chapter 5 Section C • In a microcomputer, the CPU is a single integrated circuit called a microprocessor. Page 221

Central Processing Unit Architecture What does the CPU look like? Chapter 5 Section C • The CPU has two parts • ALU (arithmetic logic unit) • performs arithmetic operations • performs logical operations • uses registers to hold data being processed • The result of an operation is place in the accumulator. • From accumulator data, it can be sent to RAM or used for further processing. Page 221

Central Processing Unit Architecture What does the CPU look like? Chapter 5 Section C • The CPU’s control unit directs and coordinates processing. • The control unit’s instructionpointer tracks sequence of instructions. • places in instructionregister Page 222

Central Processing Unit Architecture What does the CPU look like? Chapter 5 Section C play animation f0518 Page 222

Instructions What specifies the steps that the CPU must perform to accomplish a task? Chapter 5 Section C • An instruction (a series of simple steps) tells the computer to perform arithmetic, logical or control operations. • Opcode - part of the instruction which stands for operation code is a command word such as: • add • compare • jump • Operand - specify data or address of data for operation Page 223

Instructions What specifies the steps that the CPU must perform to accomplish a task? Chapter 5 Section C JMP M1 In this example JMP means jump and M1 is the RAM address of the instruction the computer is supposed to go to. • An instructionset is the list of instructions a CPU is able to execute. op code operand Page 223

Instruction Cycle How does a computer process instructions? Chapter 5 Section C • The process in which a computer executes a single instruction is called the instructioncycle. Page 224

CPU Performance Factors How does the architecture of a computer contribute to its performance? Chapter 5 Section C • CPU speed is influenced by several factors: • clock rate • word size • cache • instruction set size • A computer with a high-performance processor may have: • slow hard disk • small amount of RAM • no disk cache Page 225

Clock Rate What does the date and time have to do with CPU performance? Chapter 5 Section C • A computer’s system clock is not the same as a “real-time” clock. • Systemclock - emits pulses to establish the timing for all system operations • sets speed for data transport and instruction execution • The time it takes to complete an instruction cycle is measured in megahertz. Page 226

Word Size Which is faster, an 8-bit processor or a 64-bit processor? Chapter 5 Section C Section C • Wordsize - the number of bits that the CPU can manipulate at once. • based on size of registers in CPU • based on number of data lines in the bus Page 226

Cache Is there a process that speeds access to data from RAM? Chapter 5 Section C • Cache - special high-speed memory that gives CPU more rapid access to data • The cache ensures that data is immediately available whenever the CPU requests it. Page 226

Instruction Set Complexity What’s the difference between CISC and RISC? Chapter 5 Section C • Computers based on a CPU with a complex instruction set known as CISC (complex instruction set computer) machine. • A RISC (reduced instruction set computer) has limited set of instructions that it can perform quickly. Page 227

Pipelining and Parallel Processing Can a CPU increase its performance by executing more than one instruction at a time? Chapter 5 Section C • Computers with a single processor execute instructions serially (one at a time). • Pipelining - technology in which processor can begin executing next instruction before it completes previous instruction. Page 227

Pipelining and Parallel Processing Can a CPU increase its performance by executing more than one instruction at a time? Chapter 5 Section C • A computer with more than one processor can execute multiple instructions simultaneously, referred to as parallelprocessing. • Computers that use parallel processing are called parallelcomputers. Page 228

Section D Input/Output CHAPTER 5 Computer Architecture Page 229

Section D Input/Output Chapter 5 SectionPREVIEW Section D Section D You will be able to: • Describe how the data bus and the expansion bus work • List the components necessary to connect a peripheral device to a computer and describe each component’s role Page 229

Section D Input/Output Chapter 5 Section D You will most likely want to add equipment to your computer to expand its capabilities • I/O (computer jargon for input/output) refers to collecting data and transporting results. • Expansion bus - the segment of the data bus that transports data between RAM and peripheral devices Page 229

Section D Input/Output Chapter 5 3. Expansion slot extends the expansion bus to an expansion card Section D 4. Expansion card contains a port 1. Data originates in RAM 2. Expansion bus transports data along circuits on the motherboard. 5. Data cable plugs into the port, then leads to a peripheral device. Page 229

Expansion Slots and Cards How do I use expansion slots? Chapter 5 Section D • Expansion slot - long, narrow socket on the motherboard into which you can plug an expansion card • Expansion card - small circuit board that provides computer with ability to control storage, input or output device • Most microcomputers have 4 - 8 expansion slots. Page 230

Expansion Slots and Cards How do I use expansion slots? Chapter 5 Section D • Today’s microcomputers come with • graphicscard (for connecting monitor) • modem (for transmitting data over phone or cable lines) • soundcard (for connecting speakers) Page 230

Expansion Slots and Cards How do I use expansion slots? Chapter 5 Section D • The microcomputer motherboard typically has: • ISA - older technology, modems and slow devices • PCI - for graphics, sound, video, modem or network cards • AGP - for graphics cards • Expansion cards are built for only one type of slot. Page 231

Expansion Ports and Cables How do I connect a peripheral device to an expansion card? Chapter 5 Section D • To connect a peripheral device to an expansion card, you plug a cable from the device into the expansion port. • Expansionport - any connector that passes data in and out of a computer or peripheral device. Page 232

Computer Architecture