Overview and Big Ideas

1 September

TA: Michael Henson

Questions?

What is a Computer?

• Tape Drives?

• Big box with lots of lights?

• Display with large letters?

• Little box with no lights?

• Lump in the cable?

5 Classic Computer Components

CRT Display

LCD

Mouse

Inside the Case

Motherboard

Memory

• RAM -> Random Access Memory

• DRAM -> Dynamic Random Access Memory

• SRAM -> Static Random Access Memory

• ROM -> Read-only Memory

• Volatile / Non-Volatile -> needs power or not

• Magnetic -> stores bits as magnetized regions

Pentium III Xeon

You only need switches and wires!

Disk Drive

Improving Technology

Performance Increase

Abstractions

• What the user wanted.

• What the programmer designed.

• What the programmer thought about.

• What the language allowed.

• Assembly language.

• Binary.

• Function blocks.

• Gates

• Devices

• Physics

Abstraction: C to ASM

Abstraction: ASM to Binary

Instruction Set Archtecture

... the attributes of a computing system as seen by the programmer, i.e. the conceptual structure and functional behavior, as distinct from the organization of the data flows and controls, the logic design, and the physical implementation.[BR] – Amdahl, Blaaw, and Brooks, 1964

• interface between hardware and low-level software

• standardizes instructions, machine language bit patterns, etc.

• advantage: different implementations of the same architecture

• disadvantage: sometimes prevents using new innovations

Modern instruction set architectures: 80x86/Pentium/K6, PowerPC, DEC Alpha, MIPS, SPARC, HP

CISC versus RISC

• ISA’s originally for humans to use

• Small memory size was critical thus complex instructions

• High-level-language architectures (B5000)

• RISC says do a few things well; only supply what the compiler will use; rely on compiler to get it right.

Why look at MIPS?

Why not one that matters like Intel?

• Complexity
  Ugliness
  Horror
  Reality
  

The Really Big Ideas

• Just bits for data and program

• Program is a sequence of instruction words

• Data-type determined by instruction

• Large linear "array" of memory

• Small number of "variables" (registers)

Just Bits

• Program and data have the same representation

• Programs can manipulate programs

• Programs can manipulate themselves!

• Bits not the only way (Lisp)

Data Types

• char byte short int pointer quad float double

• Instruction determines type of operands

  • Add (int), Add.s (float), Add.d (double)

• Free to reinterpret at will

• How big is a char?

• What's a pointer?

Memory

• Large (usually) linear array

• Only read with load instructions

  • lw $t5, 100($a3) -> t5 = mem[100 + a3]

• Only modified with store instructions

  • sw $s0, 24($t3) -> mem[24 + t3] = s0

• CISC machines have lots of ways to read and write memory

Memory

• Address is always in bytes

• Words on 4 byte boundary (how man 0's?)

• Short only on 2 byte boundary

• Doubles only on 8 byte boundary

• CISC allowed them anywhere (Why?)

It's an ABSTRACTION!

GP Registers

• Variables for our programs

• The ONLY operands for most instructions

• A very small number (32 in MIPS) (Why?)

• All 32 bits

• What about new 64 bit ISA's?

Where we are headed

• Programming the MIPS ISA (Chapter 2)

• Arithmetic and how to build an ALU (Chapter 3)

• Performance issues (Chapter 4)

• Just a bit on processor implementation (Chapter 5)

• Pipelining to improve performance (Chapter 6)

• Memory Hierarchy: caches and virtual memory (Chapter 7)

Cultural Highlights

• Old Fashioned Farmer's Days at [" http://maps.google.com/maps?spn=0.407765,0.634701&saddr=chapel+hill,+nc&daddr=Snow+Camp+Rd+%26+Silk+Hope+Liberty+Rd,+Siler+City,+NC+27344&hl=en" Silk Hope]

• United We Funk: Cancelled!