Computer Operation

Binary Codes CPU operates in binary codes Representation of values in binary codes Instructions to CPU in binary codes Addresses in binary codes

Computer Architecture Input unit Main Memory ALU Control unit Output unit Backing Store Control signal Data/ Instructions

CPU Silicon chip Millions of electronic components Very large scale Integrated Circuit Speed – MHz, GHz Pentium (Intel) PowerPC (Apple/Mac) M68000 (Motorola)

Computer Organization

Speeding up processing - Pipelining

Speed of CPU

CPU and Memory The CPU fetches instructions from memory, fetches(load) data from memory, and store data back in memory after calculation. Memory consists of a large number of locations each having a unique address Each location consists of 8 bits(1 byte) The number of bits representing the addresses determines the address space (e.g. 10 bit address  1024 locations (=1K) 20 bits  1 M(?), 32 bits  4 G (?))

Main Memory (RAM) Main Memory 10-bit Address (decimal)

Machine Instructions CPU can only understand and execute machine instructions that is designed when the chip is manufactured We call the language that CPU understands ‘ Machine Language ’ All ‘ High-level language ’ programs must be translated to machine instructions before executing (e.g. Pascal  compiler  machine instructions) The whole set of machine instructions for a CPU is called Instruction Set Different CPUs have different machine instruction sets

For example For I:=1 to 10 do Sum:=sum+I Pascal statements Machine instructions  Translated to.. Pascal compiler  

Assembly language Machine language is difficult to design, debug and understand Use abbreviations(short forms) to replace machine instructions One machine instr. corresponds to one assembly instruction  assembly language e.g  LDA sum

Components of control unit Program counter (PC) Instruction register (IR) Processor status word (PSW) Instruction Decoder

Components of ALU Accumulator Arithmetic and logic operations circuits Registers