INTRODUCTION TO
COMMUNICATION
TECHNOLOGIES (ICT)
LECTURE 2 : WEEK 2
CSC-111-T
TEXT AND REF. BOOKS
Text Book:
Peter Norton (2011), Introduction to Computers, 7 /e, McGraw-Hill
Reference Book:
Gary B (2012), Discovering Computers, 1/e, South Western
Deborah (2013), Understanding Computers, 14/e, Cengage Learning
June P & Dan O (2014), New Perspective on Computer, 16/e
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Learning Outcome
◻ Components of Computer System
Motherboard, CPU (ALU, CU, Registers etc)
◻ Computer Memory and its types
Primary, Secondary, RAM, ROM, Cache, BUS etc
◻ Parts of computer system
◻ Memory Speed
◻ The Information Processing Cycle
◻ Computer Data & Users
Parts of the Computer System
◻ Computer systems have four parts
Hardware Software Data
User
Computer Hardware
◻ Computer hardware refers to the physical parts
or components
◻ Monitor, mouse, keyboard, data storage, hard drive
disk (HDD), system unit (graphic cards, sound cards, memory, motherboard and chips)
Mechanical devices in the computer Anything that can be touched
Computer Hardware
Motherboard (Main or Logic Board)
◻ The motherboard is the piece of
computer hardware that can be thought of as the "back bone" of the PC
◻ The motherboard serves to connect all of the parts
of a computer together i.e.
The CPU, memory, hard drives, optical drives, video card, sound card and other ports and expansion cards all connect to the motherboard directly or via cables
Typical Motherboard
What is a CPU ?
◻ Central processing unit (CPU) is the hardware
within a computer that carries out instructions of a computer program by performing the basic
arithmetical, logical, and input/output operations of the system
◻ More than one CPU is called multiprocessing
◻ Modern CPUs are microprocessors, contained on a single chip
◻ Some integrated circuits (ICs) can contain multiple CPUs on a single chip; called multi-core processors
CPU : 3 Major Components
◻
Arithmetic Logic Unit
(ALU)
◻
Control Unit
(CU)
◻
Registers
CPU : 3 Major Components
◻ ALU (arithmetic logic unit)
An ALU is a digital circuit used to perform arithmetic and logic operations
◻ Performs calculations and comparisons
Arithmetic (Addition, Subtraction, Multi, Division etc) Logical operations (NOT, AND, OR)
◻ Modern CPUs contain very powerful and complex ALUs
CPU : 3 Major Components
◻
CU
(control unit): performs fetch/execute
cycle
Functions:
■ Moves data to and from CPU registers and other
hardware components
■ Accesses program instructions and issues commands to
the ALU Subparts:
■ Memory management unit: supervises fetching instructions and data
Characteristics of CU
◻ In charge of all the operations being carried out
◻ Direct the system to execute instructions
◻ Communicate between the memory and the ALU
◻ Load data and instructions from the secondary
memory (HDD) to the main memory (RAM) as required
Registers
A register is a small amount of storage available as part of a CPU,
■ Data registers can hold numeric values such as integer
■ Address registers hold addresses
■ General purpose registers (GPRs) can store both
data and addresses
Registers
◻
Use of Registers
Scratchpad for currently executing program
■ Holds data needed quickly or frequently
Stores information about status of CPU and currently executing program
■ Address of next program instruction ■ Signals from external devices
Characteristics of Registers
◻ Small, permanent storage locations within the CPU
◻ Manipulated directly by the Control Unit
◻ Wired for specific function
◻ Size in bits or bytes (not MB like memory)
◻ Can hold data, an address or an instruction
◻ The more registers a CPU has available, the faster it can work
System Block Diagram
Processor Fabrication
◻ Performance and reliability of processors has
increased with improvements in materials and fabrication techniques
Transistors and integrated circuits (ICs) Microchips and microprocessors
Processor Fabrication
What is Memory ?
◻ Physical devices used to store programs (sequences
of instructions) or data on a temporary or permanent basis for use in a computer
◻ Two types of Memory Secondary Memory
Primary or Main Memory
Secondary Memory
◻ Non-volatile and persistent in nature and is not directly accessed by a processor
◻ Secondary memory is accessed only by the primary or main memory
◻ Slower than P.M but larger in size and cheap ◻ Data can be stored for later retrieval
HDD, Tape Drives etc
Primary Memory
◻ Computer memory that a processor or computer
accesses first or directly
◻ Allows a processor to access running execution
applications and services
Random Access Memory (RAM) Read Only Memory (ROM)
RAM: Random Access Memory
◻ DRAM (Dynamic RAM)
Most common, cheap
Volatile: must be refreshed (recharged with power) 1000’s of times each second
◻ SRAM (Static RAM)
Faster than DRAM and more expensive than DRAM Volatile
Frequently small amount used in cache memory for high-speed access used
RAM: Random Access Memory
ROM - Read Only Memory
◻ Non-volatile memory to hold software that is not expected to change over the life of the system
◻ EEPROM
Electrically Erasable Programmable ROM Slower and less flexible than Flash ROM
◻ Flash ROM
Faster than disks but more expensive Uses
■ BIOS: initial boot instructions and
diagnostics
Bus
◻ The physical connection that makes it possible to transfer data from one location in the computer system to another
◻ A Computer bus used to transfer data, signals or power between some of the components of computer
◻ Group of electrical conductors for carrying signals from one location to another
Line: each conductor in the bus
Bus
◻
3 kinds of signals
1. Data (alphanumeric, numerical, instructions)
2. Addresses
3. Control signals
◻
Connect CPU and Memory
Speed and Power
What makes a computer fast?
◻ Microprocessor speed
◻ Bus line size
◻ Availability of cache
◻ Flash memory
◻ Parallel processing
Computer Processing Speed
Time to execute an instruction
◻ Millisecond ◻ Microsecond
◻ Nanosecond
Modern computers
◻ Pico second
In the future
Cache Memory
◻ Small block of very fast temporary memory
◻ Speeds up data transfer
◻ Stores/keeps instructions and data used most
frequently or most recently
Types of Cache Memory
◻ Internal cache
Level 1 (L1)
Built into microprocessor Up to 128KB
◻ External cache
Level 2 (L2) Separate chips 256KB or 512 KB SRAM technology
Cheaper and slower than L1
Faster and more expensive than memory
Computer
M
emory
Computer memory is binary (0 or 1) (on or off)
The byte is the standard unit of measurement A byte is composed of 8 bits (binary digits) Typical units of measurement:
■ 1 KB (kilobyte) = 1000 bytes
■ 1 MB (megabyte) =1000 kilobytes or 1 million
bytes
■ 1 GB (gigabyte) =1000 megabytes or 1 billion
bytes
Memory Speed
◻ Cache
Level 0 (L0) Micro operations cache – 6 KiB in size
Level 1 (L1) Instruction cache – 128 KiB in size
Level 1 (L1) Data cache – 128 KiB in size. Best access speed
is around 700 GiB/second
Level 2 (L2) Instruction and data – 1 MiB in size. Best
access speed is around 200 GiB/sec
Level 3 (L3) Shared cache – 6 MiB in size. Best access speed
is around 100 GiB/second
Level 4 (L4) Shared cache – 128 MiB in size. Best access
speed is around 40 GiB/second
Memory Speed
◻
Main memory –
Gigabytes
Best access speed
is around
10 GiB/second
◻
Disk storage –
Terabytes
As of 2013, best
access speed is from a solid state drive is about
600 MiB/second
Types of Processing
◻ Serial processing
Execute one instruction at a time Fetch, decode, execute, store
◻ Parallel Processing
Multiple processors used at the same time
Can perform trillions of floating-point instructions per second (teraflops)
Ex: network servers, supercomputers
Types of Processing
Pipelining
Instruction’s
action need not be complete before the next begins
Fetch instruction 1, begin to decode and fetch
instruction 2
