Computer Organization. The Five Hardware Units General purpose computers use the "Von Neumann"...
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Transcript of Computer Organization. The Five Hardware Units General purpose computers use the "Von Neumann"...
Computer Organization
The Five Hardware Units
General purpose computers use the "Von Neumann" architecture
Also referred to as "stored program" architecture
CPU
MainMemory(RAM)
InputUnit
OutputUnit
SecondaryMemory
Central Processing Unit
Control unit – directs the operation of the rest of the computer
Arithmetic-Logic Unit – performs calculations and comparisons
Communicates via "system bus" with other components
ControlUnit
Arithmetic-LogicUnit
Central Processing Unit
System bus
Main MemoryComposed of a sequence of "cells" or "words," each composed of "bits"
Each cell has a numeric address
The contents of any cell can be retrieved or stored in the same amount of time
Thus, "Random Access Memory"
Input Unit
We need some way to get data from the outside world into the computer
Examples: Keyboard
Mouse
Microphone
Graphics tablet
Scanner
Modem/network card
Output Units
Likewise, we need a way to communicate to the outside world
Screen
Printer
Speakers
Modem/network interface
Secondary Memory
High capacity, long-term storage
Examples Hard disks
Optical drives (CD-ROM, DVD-ROM)
Flash drives
Next level is tertiary or archival storage Backup tape drives
Floppy disks
The Memory HierarchyRegisters – locations in the CPU for current
computations
Cache – very fast memory for frequently used values
Main memory – fast memory used for currently executing programs and their data
Secondary memory – slower (but very large) memory used for long term storage of programs and data
Tertiary memory – slowest (but largest) memory used for backups and archival storage
Memory Persistence
Volatile memory – memory that only works when electrical power is supplied
Registers, cache, and main memory (RAM)
Non-volatile memory – memory that retains its contents when power is off
Hard drives, flash drives, optical drives, magnetic tape
Memory access types
Read-write – data can be stored and retrieved any number of times (registers, cache, RAM)
Read-only (ROM) – contents cannot be altered
Storage DensitiesUnits
1 byte = 8 bits = space to store 1 character
1 Megabyte (MB) = 220 = 1,048,576 bytes
1 Gigabyte (GB) = 230 = 1,073,741,824 bytes
1 Terabyte (TB) = 240 = 1,099,511,627,776 bytes
ExamplesA 300 page book holds approximately 1,500,000 characters
DVD-5 format disk holds 4.7 GB of data
30 GB IPod holds 7500 4 minute songs
Dual layer Blu-ray format disks hold 50 GB of data (holds 9 hours of HD video or 23 hours of SD video)
US Library of Congress holds 20 TB of data
Memory Cost
Prices are retail consumer-oriented
512MB RAM chip – 12 cents per MB
200GB hard disk – 0.054 cents per MB
400GB hard disk – 0.041 cents per MB
(prices gathered on 9/12/06)
Assignment
How Computers Work, Chapters 1-3 and 5