Computers Central Processor Unit

Basic Computer System MAIN MEMORY ALUCNTL..... BUS CONTROLLER Processor I/O moduleInterconnections BUS Memory

Von Neumann Architecture CPU Fast Memory Slow Storage Binary Program: executed in sequence Computer behavior is determined by stored programs.

John Von Neumann and ENIAC

Computer Components Processing (CPU) Arithmetic Logic Unit Control Unit Registers Word Clock Instruction sets Interconnection Local bus Peripheral bus Primary Storage RAM/ROM Cache Input/Output Channel Controller Buffers

CPU’s

CPU Cycle Start FETCHEXECUTE Halt Increment Program Counter FETCHEXECUTE

Instruction Format Instruction: Operation Codes Operands Word: set of bits held by registers in the CPU. May contain instructions or data. OP CodeOperands 4 Bits 12 Bits

Types of Instructions Chip Instructions = Built-in Machine Instructions – “microcode” = Chip Instructions + ROM Instructions Assembler Instructions =Alphabetic Abbreviations for Machine Instructions

ROM Instructions ALUCNTL..... ROM INSTRUCTIONS (BIOS in PCs)

RISC and CISC CISC uses fewer processor cycles RISC has fewer instructions, requires more processor cycles How can RISC be faster?

Basic Computer System MAIN MEMORY ALUCNTL..... BUS CONTROLLER Processor I/O moduleInterconnections BUS Memory

Local and Peripheral Bus

Bus Operation Transfer Quantity (word) Address bus Control bus Data bus Speed Clock speed

Memory Hierarchy CACHE MAIN MEMORY MAGNETIC DISK | DISK CACHE MAGNETIC TAPE | OPTICAL DISK SPEEDCOST REGISTERS

Capacity Units Bit Byte Kilobyte Megabyte Gigabyte Terabyte b B = 8 b KB = 1,000 B MB = 1,000,000 B GB = 1,000,000,000 B TB = 1,000,000,000,000 B

Memory Access Method Sequential - tape Direct - floppy or hard disk Random - internal memory Dynamic (DRAM) simple, small, must be refreshed Static (SRAM) no refresh needed

Random Access Memory Chips and chip technology

Flip Flop Circuit Diagram

DASD Access MAIN MEMORY DASD BUFFER CONTROLLER CPU CACHE

Representative Times Network speed = megabits per second Disk transfer = megabytes per second Disk access = milliseconds Memory access = nanoseconds Machine cycle = microseconds/nanoseconds

DASD (direct access storage device) Read-Write Heads

Cylinder/Track/Block Block (Sector)Track Cylinder

Data Storage FAT (File Access Tables), Directories and Catalogs Update and Delete Fragmentation and reorganization Blocks, Headers and Interblock Gaps

What makes a computer run? Word size Instruction set Bus speed Main memory Secondary storage Buffers and cache

IBM 1107 with tape drives

Operating Systems PROGRAM HARDWARE OPERATING SYSTEM

System Structure Layers Processor Hardware functions: circuits, instruction set, procedures, interrupts Process management: multiprogramming, management of secondary storage, logical addressing External resource management: communication among process, file management, device access and addressing, user support

Virtual Memory PAGE NUMBER + OFFSET FRAME NUMBER + OFFSET Page Frames Pages PAGE TABLE PAGE TABLE PAGE TABLE

Comparison MVS versions (OS/390) UNIX Windows NT Linux