Computers

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Computers

• Central Processor Unit

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Basic Computer System
Processor
ALU
CNTL
.....
I/O module
BUS
CONTROLLER
MAIN MEMORY
BUS
Memory
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Von Neumann Architecture

• CPU
• Fast Memory
• Slow Storage
• Binary Program executed in sequence
• Computer behavior is determined by stored
  programs.

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John Von Neumann and ENIAC
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Computer Components

• Processing (CPU)
• Arithmetic Logic Unit
• Control Unit
• Registers
• Word
• Clock
• Instruction sets
• Interconnection
• Local bus
• Peripheral bus

• Primary Storage
• RAM/ROM
• Cache
• Input/Output
• Channel
• Controller
• Buffers

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CPUs
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CPU Cycle
Increment Program Counter
FETCH
EXECUTE
FETCH
EXECUTE
Halt
Start
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Instruction Format
4 Bits
12 Bits
OP Code
Operands

• Instruction
• Operation Codes
• Operands
• Word set of bits held by registers in the CPU.
  May contain instructions or data.

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Types of Instructions

• Chip Instructions
• Built-in
• Machine Instructions microcode
• Chip Instructions
• ROM Instructions
• Assembler Instructions
• Alphabetic Abbreviations for Machine
  Instructions

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ROM Instructions
INSTRUCTIONS (BIOS in PCs)
ROM
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RISC and CISC

• CISC uses fewer processor cycles
• RISC has fewer instructions, requires more
  processor cycles
• How can RISC be faster?

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Basic Computer System
Processor
ALU
CNTL
.....
I/O module
BUS
CONTROLLER
MAIN MEMORY
BUS
Memory
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Local and Peripheral Bus
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Bus Operation

• Transfer Quantity (word)
• Address bus
• Control bus
• Data bus
• Speed
• Clock speed

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Memory Hierarchy
SPEED
COST
REGISTERS
CACHE
MAIN MEMORY
MAGNETIC DISK DISK CACHE
MAGNETIC TAPE OPTICAL DISK
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Capacity Units

• Bit
• Byte
• Kilobyte
• Megabyte
• Gigabyte
• Terabyte

• b
• B 8 b
• KB 1,000 B
• MB 1,000,000 B
• GB 1,000,000,000 B
• TB 1,000,000,000,000 B

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Memory Access Method

• Sequential - tape
• Direct - floppy or hard disk
• Random - internal memory
• Dynamic (DRAM)
• simple, small, must be refreshed
• Static (SRAM)
• no refresh needed

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Random Access Memory

• Chips and chip technology

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Flip Flop Circuit Diagram
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DASD Access
MAIN MEMORY
CPU
BUFFER
CACHE
DASD
CONTROLLER
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Representative Times

• Network speed megabits per second
• Disk transfer megabytes per second
• Disk access milliseconds
• Memory access nanoseconds
• Machine cycle microseconds/nanoseconds

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DASD (direct access storage device)
Read-Write Heads
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Cylinder/Track/Block
Block (Sector)
Track
Cylinder
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Data Storage

• FAT (File Access Tables), Directories and
  Catalogs
• Update and Delete
• Fragmentation and reorganization
• Blocks, Headers and Interblock Gaps

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What makes a computer run?

• Word size
• Instruction set
• Bus speed
• Main memory
• Secondary storage
• Buffers and cache

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IBM 1107 with tape drives
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Operating Systems
PROGRAM
HARDWARE
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System Structure Layers

• Processor Hardware functions circuits,
  instruction set, procedures, interrupts
• Process management multiprogramming, management
  of secondary storage, logical addressing
• External resource management communication among
  process, file management, device access and
  addressing, user support

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Virtual Memory
FRAME NUMBER OFFSET
PAGE NUMBER OFFSET
PAGE TABLE
PAGE TABLE
PAGE TABLE
Page Frames
Pages
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Comparison

• MVS versions (OS/390)
• UNIX
• Windows NT
• Linux