Computer Technology History

1
Computer Technology History

• Switches Devices that can be flipped between 2
  states
• Binary numbers two states (0, 1)
• Vacuum tubes
• first switches used in computers
• allow or block flow of electrical current
• take up a lot of space
• Transistors
• built out of semiconductors
• either conduct electricity or act as insulators
• Chips (Integrated circuits)
• small region of semiconductor that supports many
  transistors
• importance? designers create small yet
  powerful microprocessors

2
Today What is .?

• A Computer?
• hardware
• software
• A Computer System?
• hardware / software / resources / people
• The Processing Cycle (IPOS)?
• Input / Processing / Output / Storage
• converts data into information
• includes primary, secondary storage
• Functions of the IPOS?
• input / output
• storage / retrieval
• calculations
• logic / comparison

3
Processing Data What Makes A Computer Compute?

• How Data is Stored
• How Data is Processed
• Central Processing Unit (CPU)
• Memory / Storage

4
How Is Data Stored?

• Address (storage location)
• each address holds one piece of data
• computer assigns address and stores data until
  replaced by new data
• read/write concept
• Binary System (bits, bytes)
• Bit smallest storage unit represented by 1s,
  0s
• ASCII coding schemes
• example D 1000100
• Byte 1 character (8 bits)
• computers storage capacity is measured in bytes
• Kilobytes (kb) Megabytes (mb)
• Gigabytes (gb) Tetrabytes (trillion)

5
CPU What's Inside?

• Control Unit
• manages the switches inside the CPU
• remembers processing stages sequence
• moves switches to correct setting (ON / OFF)
• performs work of that stage
• Arithmetic-Logic Unit (ALU)
• processes calculations
• performs logic / comparison functions
• Relational and Logical operators
• data is not stored in ALU
• Registers
• Temporary storage locations

6
CPU (Central Processing Unit)

• Brains of the computer
• microprocessor technology
• found on main circuit board (motherboard)
• executes instructions
• examples pentium4, PowerPC-G5
• How to measure differences in processing power?
• number of transistors on CPU
• clock speed determines movement from one stage
  of the CPU cycle to the next
• cache memory

7
How Data is Processed CPU Machine Cycle
fetch
(Control unit from memory)
decode
store
Control unit converts to machine language
Registers, Cache results
execute
ALU decision, logic, math
8
Fetch Stage
fetch

• Instructions are moved to the CPU
• Information sources
• instructions from RAM or Cache are moved into
  registers
• registers are faster than RAM or Cache and
  located on the CPU
• Cache memory
• holds recent or frequently used data/instructions
• on the CPU chip or near it
• cannot be upgraded
• L-1, L-2, L-3

9
Decode Stage
decode

• program instructions are translated into commands
  the CPU understands and can execute (Instruction
  Set)
• Assembly language language used by programmers
  to define the instruction set of a CPU
• Machine language
• Binary code for computer instructions
• Assembly language commands are translated into
  long strings of bits (binary language)

10
Execute Stage / Store Stage

• Execute ALU (arithmetic logic unit) performs
  math and logical operations
• Add, subtract, compare, etc.
• AND, OR, NOT
• ALU is fed data from CPU registers
• Word size Number of bits a computer can work
  with at a time (32 bit, 64 bit)
• Store Computation results stored in registers

execute
store
11
Random Access Memory (RAM)

• Volatile data is erased when power is
  interrupted
• Typical amounts 256Mb, 512 Mb, 1Gb
• Access time
• Time required for a device to access data and
  instructions and make them available to the CPU
• Access time of RAM is much smaller than access
  time of hard disk
• Types DRAM, SRAM
• SRAM much faster

memory
12
Buses The CPUs Data Highway

• Bus
• Electrical pathway used to move data between
  components
• Local bus Connects the CPU with the memory
• Expansion bus Connects the CPU with peripheral
  devices

01100010
01001000
01110011
00100111
13
Bus Performance

• Bus clock speed
• rate of speed data moves from one location to
  another
• measured in MHz (millions of clock cycles per
  second)
• Bus width
• the number of bits of data moved on a bus at any
  one time
• measured in bits 16, 32, 64
• results in increased processing speed

14
Making Computers Faster

• Pipelining CPU processes more than one
  instruction at a time accesses new instruction,
  adjacent data before previous instruction is
  finished

Nonpipelined CPU
Instruction 1
Fetch
Decode
Execute
Store
Instruction 2
Fetch
Decode
Execute
Store
Pipelined CPU
Fetch
Decode
Execute
Store
Instruction 1
Fetch
Decode
Execute
Store
Instruction 2
Fetch
Decode
Execute
Store
Instruction 3
Fetch
Decode
Execute
Store
Instruction 4
15
Moores Law

• Number of transistors on a CPU will double every
  18 months
• First chip (8086) had 29,000 transistors
• Pentium chip 169,000,000 transistors
• Moores Law has been accurate for more than 40
  years
• Law has remained accurate into the 21st century