The document provides an introduction to computer architecture. It discusses binary numbers and the bit and byte units used to measure digital information. It describes the major components of a computer system, including the central processing unit (CPU), memory, hard drives, and input/output components. The CPU functions are explained, including fetching and executing instructions through a cycle and using registers, caches, and memory in a hierarchy. Direct access memory like RAM is faster than sequential access storage like hard disks.

1. Introduction to Computer
Architecture
Ankush Srivastava
Email:- anksri000@gmail.com

2. What is binary?
 We use the decimal (base 10) number
system
 Binary is the base 2 number system
 Ten different numbers are used in
base 10. How many are used in base
2?

3. Bits & Bytes
 kilo, mega, and giga are different in
binary!
bit (b) – binary digit
Byte (B) – 8 binary digits
KiloByte (KB) – 210 bytes
MegaByte (MB) – 220 bytes
GigaByte (GB) – 230 bytes

4. Storage Scam!
 Example: iPod Nano 8GB

5. 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...

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

7. ON-OFF-ON-ON
1 0 1 1
 Several ways to remember the state of a switch:
 Electrical – RAM, flash memory
 Magnetic – Hard drives, magnetic tapes
 Optical – CDs, DVDs

8. What does memory look like?
Address Data
 Memory ~ RAM 0 36
 Looks like a table 1 3765
 Address and Data 2 786
 Address is the 3 356
location 4 252
 Data is the actual 5 67980
value 6 2355
 Memory stores both 7 4234
data and assembly 8 3466
instructions

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

10. Fetch-Execute Cycle
1. Fetch instruction from
memory
2. Decode instruction in Control
Address Bus
control unit
Unit
Memory
3. Execute instruction (data ALU
Data Bus
may be fetched from
memory)
4. Store results if necessary
5. Repeat!

11. Registers
 Temporary storage containers used
inside the CPU
 Extremely fast
 Fixed size, usually multiples of 8-bits
 Also called a “word”
 Example: 32-bit machines (4-byte words)
 How large is a word in a 64-bit
machine?

12. 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

13. Memory Hierarchy

14. 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

15. Hard Drives

16. CD/DVDs
 Lands and pits used to represent
binary
 Optical medium - lasers and refraction
used to read lands and pits

17. Direct Access
 also known as “random access”
 No need to go through other data to get
the data you want
 We already know where the data is, so
we just get it
 “Magic data retrieval” – no
movement/motion
 Example: registers, cache, RAM

18. Sequential Access
 also known as “serial-access”
 Data is ordered in some sequential
fashion
 To get to your data, you need to go
through other data in front of it
 Example:
 Fast-forwarding through a tape to get to
the song you want

19. Direct-Access vs. Sequential Access
 Direct-Access:
 Advantage: fast access
 Disadvantage: data cannot be accessed in sequential or sorted
order
 Data is placed randomly on the disk
 Accessing things in order then requires an index file
 Slower when trying to access sequential data that is not already in
order (back-and-forth-and-back-and-forth)
 Example: hard drives (disks)
 Sequential Access
 Advantage: Simple to organize (already in some sequential
order)
 Disadvantage: Slow when accessing specific things in no order
 Example: magnetic tape backups
 Could we implement sequential access using a hard
disk?