The CPUThe CPU

(or Central Processing Unit(or Central Processing Unit

StatisticsStatistics

Clock speedClock speed – number of instructions that – number of instructions that can be executed per secondcan be executed per second

Data widthData width – The number of bits held in – The number of bits held in each registereach register

Number of TransistorsNumber of Transistors – The electronic – The electronic component that makes computation component that makes computation possiblepossible

Multi-CoreMulti-Core

Multiple processors on one chipMultiple processors on one chip

Examples: Dual-core or Quad-coreExamples: Dual-core or Quad-core

Supercomputers have many processorsSupercomputers have many processors

Cannot increase speed indefinitelyCannot increase speed indefinitely– One calculation depending upon previous oneOne calculation depending upon previous one

Moore’s LawMoore’s Law

““The number of transistors that can be placed inexpensively on an The number of transistors that can be placed inexpensively on an

integrated circuit has doubled approximately every two years”integrated circuit has doubled approximately every two years” (http://en.wikipedia.org/wiki/Moore's_law)(http://en.wikipedia.org/wiki/Moore's_law)

Has leveled off in recent years due to not Has leveled off in recent years due to not being able to squeeze more transistors being able to squeeze more transistors onto a chiponto a chip

Components InsideComponents Inside

RegistersRegisters – hold data or instructions – hold data or instructions

ClockClock – tells the CPU when to execute the – tells the CPU when to execute the next instructionnext instruction

ALUALU – Does the math – Does the math

Address BusAddress Bus – Sends an address to RAM – Sends an address to RAM or ROMor ROM

Data BusData Bus – Sends data to or from RAM or – Sends data to or from RAM or ROMROM

Special RegistersSpecial Registers

Instruction RegisterInstruction Register – holds the current – holds the current instruction (example – add or subtractinstruction (example – add or subtractProgram CounterProgram Counter – holds the address of – holds the address of the next instruction to be executedthe next instruction to be executedALU has three registersALU has three registers– 2 for input2 for input– 1 for output1 for output– Always takes 2 inputs, does an operation, and Always takes 2 inputs, does an operation, and

sends it to outputsends it to output