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Computer Architecture – An Introduction

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Overview on high-level design of internal components of a computer. Cover step-by-step execution of a program through ALU while accessing & updating registers

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Computer Architecture – An Introduction

  1. 1. Computer Architecture – An Introduction CS2052 Computer Architecture Computer Science & Engineering University of Moratuwa Dilum Bandara Dilum.Bandara@uom.lk
  2. 2. From Outside 2 Input Output Processor Memory Hard disk DVD ROM Graphics card Ethernet Source: techwench.com
  3. 3. From Outside (Cont.) Source: Daniel Zanetti, wikimedia.org 3 Source: Amazon.com Touch pad Touch screen Wireless Screen size Weight Battery capacity SD Card slot Sensors
  4. 4. From Inside Source: http://rays-place.net 4 Source: http://news.techgenie.com
  5. 5. From Inside (Cont.) 5 Source: www.laptopaid.com Source: http://techgoesboom.com
  6. 6. From Inside (Cont.) 6 iPhone 6
  7. 7. What We Are Going To Study?  How these internal components look like?  Top-down approach with schematics  How do they fit together?  How to program them?  How to improve their performance? 7
  8. 8. Very High-Level View of a Computer  CPU – execute instructions  Memory – store program & data System Bus  IO devices – receive inputs & produce outputs  Bus – interconnects everything by transferring data 8 Central Processing Unit (CPU) Main Memory Input/output (IO) Devices
  9. 9. Blocks of a Microprocessor 9 Program Memory Instruction Register STACK Program Counter Instruction Decoder Timing, Control, & Register selection Accumulator RAM & Data Registers ALU IO IO FLAG & Special Purpose Registers Source: Makis Malliris & Sabir Ghauri, UWE
  10. 10. Blocks of a Microprocessor (Cont.) 10 Literal Address Operation Program Memory Instruction Register Address STACK Program Counter Instruction Decoder Timing, Control and Register selection Accumulator RAM & Data Registers ALU IO IO FLAG & Special Function Registers Clock Reset Interrupts Program Execution Section Register Processing Section Set up Set up Modify Internal data bus Source: Makis Malliris & Sabir Ghauri, UWE
  11. 11. Arithmetic & Logic Unit (ALU)  Data processing unit  Arithmetic unit  Performs arithmetic operations  Logic unit  Performs logical operations 11 Accumulator Source: Introduction to PIC Microcontroller – Part 1 by Khan Wahid
  12. 12. Registers  Type of memory located inside CPU  Can hold a single piece of data  This data is useful in both data processing & control functionalities  Several types of CPU registers  Program Counter (PC)  Instruction Register (IR)  Accumulator or working register  Special purpose registers  Flag register  General purpose registers 12
  13. 13. Program Counter (PC)  Used to keep track of memory address of next instruction to be executed  When instructions are fetched, always instruction pointed by PC is fetched into CPU  Once the instruction is fetched, PC is updated to point to next instruction  PC = PC + d 13
  14. 14. Instruction Register (IR)  Once fetched, instructions are stored in IR for execution  Located closely to control unit which decodes the instruction 14
  15. 15. Accumulator (A) / Working Register (W)  Results of arithmetic & logical operations always go to accumulator  Connected directly to output of ALU 15 Source: Introduction to PIC Microcontroller – Part 1 by Khan Wahid
  16. 16. FLAG/STATUS Register  Individual bits Indicate status of ALU operations Source: www.plantation-productions.com/Webster/www.artofasm.com/Linux/HTML/RealArithmetic.html 16
  17. 17. 17 Internal Structure B C D E ALU A Address Bus PC IR ALU Control Unit FLAG +1 CTRL Bus Data Bus Source : Dr. Chathura de Silva, CSE, UoM
  18. 18. 18 Sample Program 100: Load A,10 101: Load B,15 102: Add A,B 103: STORE A,[20] Load A,10 Load B,15 ADD A,B STORE A,[20] 100 101 102 103 104 105 Program memory 18 19 20 21 00 00 00 00 Data memory
  19. 19. 19 Instruction Execution Sequence 1. Fetch next instruction from memory to IR 2. Change PC to point to next instruction 3. Determine type of instruction just fetched 4. If instruction needs data from memory, determine where it is 5. Fetch data if needed into register 6. Execute instruction 7. Go to step 1 & continue with next instruction
  20. 20. 20 Before execution of 1st fetch cycle B C D E ALU A Address Bus 100 IR ALU Control Unit FLAG +1 CTRL Bus Data Bus Source: Dr. Chathura de Silva, CSE, UoM
  21. 21. 21 After 1st fetch cycle … B C D E ALU A Address Bus 101 ALU Load A,10 Control Unit FLAG +1 CTRL Bus Data Bus
  22. 22. 22 After 1st instruction cycle … B C D E ALU 10 Address Bus 101 ALU Load A,10 Control Unit FLAG +1 CTRL Bus Data Bus
  23. 23. 23 Sample Program (Cont.) 100: Load A,10 101: Load B,15 102: Add A,B
  24. 24. 24 After 2nd fetch cycle … B C D E ALU A Address Bus 102 ALU Load B,15 Control Unit FLAG +1 CTRL Bus Data Bus
  25. 25. 25 After 2nd instruction cycle … 15 C D E ALU 10 Address Bus 102 ALU Load B,15 Control Unit FLAG +1 CTRL Bus Data Bus
  26. 26. 26 Sample Program (Cont.) 100: Load A,10 101: Load B,15 102: Add A,B
  27. 27. 27 After 3rd fetch cycle … 15 C D E ALU 10 Address Bus 103 ALU ADD A,B Control Unit FLAG +1 CTRL Bus Data Bus
  28. 28. 28 After 3rd instruction cycle … 15 C D E ALU 25 Address Bus 103 ALU ADD A,B Control Unit FLAG +1 CTRL Bus Data Bus
  29. 29. Architectural Differences  Length of microprocessors’ data word  4, 8, 16, 32, 64, & 128 bit  Speed of instruction execution  Clock rate & processor speed  Size of direct addressable memory  CPU architecture  Instruction set  Number & types of registers  Support circuits  Compatibility with existing software & hardware development systems 29
  30. 30. Microprocessor vs. Microcontroller  Microprocessor – CPU & various IO functions are packed as separate ICs  Microcontroller – Most IO functions are integrated into same package with CPU 30 Program Memory Microprocessor Clock Data Storage I/O I/O I/O Program Memory Microprocessor Core Real-time Clock I/O I/O I/O Data Storage
  31. 31. Programming Hierarchies 31 Source: Introduction to PIC Microcontroller – Part 1 by Khan Wahid
  32. 32. Programming Language Levels  Machine code (40s-50s)  0001000000111000 0001001000110100  0101110000000000  0001110000000000 0001001000110101  Hex notation (50s-60s)  1038 1234  5C00  1E00 1235 Source: http://mentalfloss.com/article/53160/meet- 32 refrigerator-ladies-who-programmed-eniac
  33. 33. Programming Language Levels (Cont.)  Assembler  Machine code (60s-70s) .define const = 6 num1: .byte [1] num2: .byte [2] move.b num1,d0 addq.b #const,d0 move.b d0,num2  High-level languages  C code fragment (70s-80s) #define const 6 int num1, num2; num2 = num1 + const; 33
  34. 34. When is Assembler Appropriate?  Parts of a program where absolute speed is critical  More effective use of CPU registers & instruction set  Can produce code that runs faster than that produced by a compiler  There may be no other way to access a particular feature of hardware  Compiler might not provide library functions to access IO ports or to disable/enable interrupts  Compiler might not take advantage of CPU special instructions  BCD arithmetic, binary-ASCII conversion, table lookups, high speed copying of entire blocks of data 34
  35. 35. Building Digital Solutions to Computational Problems 35  Labs & design project  Product specs  Algorithms, RTL, etc.  Flowcharts  State transition diagrams  Logic equations  Circuit schematics  Verilog or VHDL code  Assembler  C, C++  TTL Gates (AND, OR, XOR ... )  Programmable Logic  Custom ASICs  FPGAs  MCs, DSPs
  36. 36. Real-World Performance Metrics  Commercial digital designs seek the most appropriate trade-offs for the target application  Time-to-market is also very important 36 Cost Commodity Products Speed Scientific Computing, Simulation Energy Portable Devices Capacity Multimedia, Scientific Computing, Simulation

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