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Instruction Set Architecture

Instruction Set Architecture

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Instruction Set Architecture

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  1. Instruction Set Architecture Stephen Murphy

  2. What is ISA? Aspects of the computer visible to the programmer: • Data Types • Registers • Instructions • Addressing

  3. Data Types • Unsigned Integers • Signed Integers • Characters • Floating-point Numbers

  4. Unsigned Integers • Stores the integer in standard binary format 00101011 = 1 + 2 + 8 + 32 = 43

  5. Signed Integers • Stores the integer in two’s complement format to denote sign Steps to convert signed integer to base 10: • Store leading bit, 1 = negative, 0 = positive • Invert all bits • Add 1

  6. Characters • Represented by integer values Many different character encodings exist: • ASCII • UNICODE • UTF-8 • UTF-16

  7. Floating-point Numbers Four components in a floating-point number: • Sign • Mantissa • Radix • Exponent

  8. Registers Registers provide a variety of services: • Instruction Counter • Register-to-Register Operations • Memory-to-Register Operations • Memory-to-Memory Operations • Processor Status

  9. Instruction Counter Register • All von Neumann machines have an instruction counter which is a register

  10. Register-to-Register Registers • Operate on one register using another register (ADD) • Supported by all ISA’s

  11. Memory-to-Register Registers • Operate on memory using a register (LOAD, STORE) • Not supported by all ISA’s

  12. Memory-to-Memory Registers • Operate on one memory location using another memory location (STRCMP) • Not supported by all ISA’s

  13. Processor Status Registers • A collection of registers that indicate the current state of the processor (Carry, Interrupt, Zero) • Different ISA’s use different status registers

  14. Instructions Categories of instructions: • Operate • Memory Access • Control • Miscellaneous

  15. Operate Instructions Typical operations include: • Arithmetic (ADD, SUB, MUL, DIV) • Logical (AND, OR, NOT, XOR) • Shift (ROL, ROR) • Character (STRCMP) • Stack (PUSH, POP)

  16. Memory Access Instructions Typical operations include: • Load (LODSB) • Store (STOSB)

  17. Control Instructions • Conditional Branch (JZ, JC, JO, JS) • Unconditional Branch (JMP)

  18. Miscellaneous Instructions • Input/Output (IN, OUT) • Interrupts (CLI, INT, IRET) • Halt • Privileged

  19. Addressing • Register Addressing • Memory Addressing

  20. Register Addressing • When an operand is taken from a register it is called register addressing

  21. Memory Addressing • Logical Address Space (sequential memory locations) • Physical Address Space (many types exists: absolute addressing, indirect addressing, etc.)

  22. ISA Examples • MIPS • Motorola 6800 • ARM • SPARC • PowerPC • x86 • IA-64

  23. ISA Humor • BOB – Branch On Bug • ADN – Add Nauseam • BPDI – Be Polite, Don’t Interrupt • BPE – Bypass Program Error • DMNS – Do what I Mean, Not what I Say • DC – Divide and Conquer • CDHI – Crash Disk Head Immediately

  24. References • http://webster.cs.ucr.edu/AoA/Windows/HTML/ISA.html • http://www.wordiq.com/definition/Instruction_set • http://www.cs.panam.edu/~meng/Course/CS4335/Notes/master/node22.html