1. Introduction to Computer Architecture

2. What is computer architecture?
What does “architecture” mean?
Layout and interactions of a computer system
What is a computer system?
Input  Process  Output
Can a computer system be more than one computer? Think of an example...

3. Major Components of a Computer
Central Processing Unit (CPU)
Random Access Memory (RAM) / Memory
Hard Drive / Disk

4. Central Processing Unit (CPU)
Also called the “chip” or “processor”
The brain of the computer
Major components:
Arithmetic Logic Unit (ALU)
calculator
Control unit
controls the calculator
Communication bus systems
What’s a bus?!?
Address Bus
Control Unit
Memory
ALU
Data Bus

5. What does memory look like?
Note: Bits in memory ardatae both values and program instructions

6. What does memory look like?
Address
Data 36 1
3765 2
786 3
356 4
252 5
67980 6
2355 7
4234 8
3466
Memory ~ RAM
Looks like a table
Address and Data
Address is the location
Data is the actual value
Memory stores both data and assembly instructions

7. Fetch-Execute Cycle (Machine Instruction Cycle)
Fetch instruction from memory
Decode instruction in control unit
Execute instruction (data may be fetched from memory)
Store results if necessary
Repeat!
Address Bus
Control Unit
Memory
ALU
Data Bus

8. ON-OFF-ON-ON 1 0 1 1 Several ways to remember the state of a switch:
Several ways to remember the state of a switch:
Electrical – RAM, flash memory, solid state drives, some ROMs
Magnetic – Hard drives, magnetic tapes
Optical – CDs, DVDs, Blu-Ray

9. Primary Memory Memory level CPU accesses closest
RAM ~ Random Access Memory
Volatile storage (data is NOT saved when computer is off)
Used to store everything (OS, programs, etc.) while computer is on
ROM ~ Read-Only Memory
Non-volatile storage
Often holds the computer’s BIOS (Basic Input/Output System) when computer first loads

10. Registers Temporary storage containers used inside the CPU
Extremely fast
MAR ~ Memory Address Register
Holds the address of where you are fetching from
MDR ~ Memory Data Register
Holds the data that was fetched from memory
Many other registers too (for all CPU calculations)

11. Fetch-Execute Cycle (Machine Instruction Cycle)
Fetch instruction from memory
Decode instruction in control unit
Execute instruction (data may be fetched from memory)
Store results if necessary
Repeat!
Address Bus
Control Unit
Memory
ALU
Data Bus

12. Fetch-Execute Animation

13. Memory Hierarchy

14. Memory Hierarchy Updated

15. Cache Slower than registers Faster than RAM
Located in front of main RAM
Different levels of cache
Level1 (L1) and Level2 (L2)
Size is usually around 1 MB

16. Virtual Memory What if a program is too big for RAM?
If a program is too big for memory (RAM), then we start using the hard drive (disk) to store data
Prevents the computer from stalling/crashing (BUT IT IS SLOW)

17. Hard Drives Persistent storage Non-volatile storage Why do we need it?
Other types of persistent storage?

18. CD/DVD/BluRays Lands and pits used to represent binary
Optical medium - lasers and refraction used to read lands and pits