Computer Organization and CPU Functions

Computer System Components

• Main Memory: stores data
• I/O: moves data between the computer and its external environment
• System Interconnection: provides communication among CPU, main memory, and I/O (e.g., System bus)

CPU Structure

• Control Unit: controls the operation of the CPU and hence the computer
• ALU (Arithmetic Logic Unit): performs the computer's data processing functions
• Registers: provides internal storage to the CPU
• CPU Interconnection/Internal bus: enables communication among the control unit, ALU, and registers

Control Unit Structure

• Sequencing: determines the sequence of operations
• Logic: performs logical operations
• Registers: provides internal storage to the CPU
• Decoders: decode instructions

CPU Organization

• Registers: temporary storage for data
• ALU: performs arithmetic and logical operations
• Control Unit: controls the operation of the CPU

Memory

• Address: a unique identifier for a memory location
• Content: the data stored at a memory location

Input/Output

• I/O Module: controls the flow of data between the CPU and I/O devices
• I/O Devices: peripherals such as keyboards, displays, and storage devices

Computer Systems Hierarchy

• A digital computer solves problems by executing instructions
• A program: a sequence of instructions describing how to perform a task

IAS (Instruction Address Register) Details

• 1000 x 40-bit words: the memory capacity of the IAS
• Set of registers: storage in the CPU
• Memory Buffer Register (MBR), Memory Address Register (MAR), Instruction Register (IR), Instruction Buffer Register (IBR), Program Counter (PC), Accumulator (AC), Multiplier Quotient (MQ): registers used in the IAS

Evolution of Intel Microprocessors

• 1970s: 4004, 8008, 8080, 8086, and 8088 processors
• 1980s: 80286, 80386, 486, and Pentium processors
• 1990s: Pentium Pro, Pentium II, and Pentium III processors
• Key features: clock speed, bus width, number of transistors, addressable memory, and virtual memory

Pentium Evolution

• 8080: first general-purpose microprocessor
• 8086: 16-bit, introduced instruction cache and prefetch
• 80286: 16 MB memory addressable
• 80386: 32-bit, supported multitasking
• Pentium II: MMX technology for graphics and multimedia processing
• Pentium III: additional floating-point instructions for 3D graphics
• Pentium 4: further floating-point and multimedia enhancements

Performance Enhancements

• Pipelining: breaking down instructions into stages to improve execution
• On-board cache: storing frequently accessed data in fast memory
• Branch prediction: predicting the outcome of conditional instructions
• Data flow analysis: analyzing the flow of data between instructions
• Speculative execution: executing instructions before it is known whether they are needed

Performance Mismatch

• Processor speed increases, but memory speed lags behind
• Solutions: increase number of bits retrieved at once, change DRAM interface, reduce frequency of memory access, and increase interconnection bandwidth

I/O Devices

• Peripherals with intensive I/O demands
• Solutions: caching, buffering, higher-speed interconnection buses, and multiple-processor configurations

Key is Balance

• Balance between processor components, main memory, I/O devices, and interconnection structures is crucial for optimal performance

Improvements in Chip Organization and Architecture

• Increase hardware speed of processor
• Increase size and speed of caches
• Change processor organization and architecture to increase effective speed of execution

Problems with Clock Speed and Logic Density

• Power consumption and heat dissipation
• RC delay: resistance and capacitance of metal wires
• Memory latency: memory speeds lag behind processor speeds

Intel Microprocessor Performance

• Increased cache capacity: more cache on chip, faster cache access
• More complex execution logic: parallel execution of instructions, pipelining, and superscalar execution

Diminishing Returns

• Internal organization of processors becomes increasingly complex
• Benefits from cache are reaching their limit
• Increasing clock rate runs into power dissipation problems

New Approach – Multiple Cores

• Multiple processors on a single chip
• Larger shared cache
• Benefits: increased performance, improved power management, and increased cache capacity