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# Introduction to Computer Architecture

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### Introduction to Computer Architecture

1. 1. Introduction to ComputerArchitecture Ankush Srivastava Email:- anksri000@gmail.com
2. 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. 3. 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
4. 4. Storage Scam! Example: iPod Nano 8GB
5. 5. What is computerarchitecture? 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. 6. Major Components of a Computer Central Processing Unit (CPU) Random Access Memory (RAM) Hard Drive / Disk
7. 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. 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. 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. 10. Fetch-Execute Cycle1. Fetch instruction from memory2. Decode instruction in Control Address Bus control unit Unit Memory3. Execute instruction (data ALU Data Bus may be fetched from memory)4. Store results if necessary5. Repeat!
11. 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. 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. 13. Memory Hierarchy
14. 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. 15. Hard Drives
16. 16. CD/DVDs Lands and pits used to represent binary Optical medium - lasers and refraction used to read lands and pits
17. 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. 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. 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?