Introduction to Computer Architecture
Lecture :- 1Date :- 15/02/11
Designed by :- Er Sanjay Agal
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?
Designed by Sanjay Agal
Bits & Bytes
kilo, mega, and giga are different in binary!
bit (b) – binary digitByte (B) – 8 binary digitsKiloByte (KB) – 210 bytesMegaByte (MB) – 220 bytesGigaByte (GB) – 230 bytes
Designed by Sanjay Agal
Storage Scam!
Example: iPod Nano 8GB
Designed by Sanjay Agal
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...
Designed by Sanjay Agal
Major Components of a Computer
Central Processing Unit (CPU) Random Access Memory (RAM) Hard Drive / Disk
Designed by Sanjay Agal
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
Designed by Sanjay Agal
What does memory look like?
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
Address Data0 361 37652 7863 3564 2525 679806 23557 42348 3466
Designed by Sanjay Agal
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?!?
Control Unit
ALU
Memory
Address Bus
Data Bus
Designed by Sanjay Agal
Fetch-Execute Cycle
1. Fetch instruction from memory
2. Decode instruction in control unit
3. Execute instruction (data may be fetched from memory)
4. Store results if necessary5. Repeat!
Control Unit
ALU
Memory
Address Bus
Data Bus
Designed by Sanjay Agal
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?
Designed by Sanjay Agal
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 Designed by Sanjay Agal
Memory Hierarchy
Designed by Sanjay Agal
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
Designed by Sanjay Agal
Hard Drives
Designed by Sanjay Agal
CD/DVDs Lands and pits used to represent
binary Optical medium - lasers and refraction
used to read lands and pits
Designed by Sanjay Agal
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
Designed by Sanjay Agal
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
Designed by Sanjay Agal
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? Designed by Sanjay Agal