Computers8 Ch4 3

Mongolia International University

Chapter 4Chapter 4

B.M.HB.M.H

The Central Process The Central Process Unit Unit

Computers MIU

Learning ObjectivesLearning Objectives

List the measures of computer List the measures of computer processing speed and explain the processing speed and explain the approaches that increase speed.approaches that increase speed. Microprocessor speedMicroprocessor speed Memory cacheMemory cache Flash memoryFlash memory RISC computersRISC computers Parallel processingParallel processing

P4-116

Computers MIU

What makes a computer What makes a computer fast?fast?

FactorsFactors Microprocessor speedMicroprocessor speed Bus line sizeBus line size Availability of cacheAvailability of cache ( More sophisticated ones )( More sophisticated ones ) Flash memoryFlash memory RISC computersRISC computers Parallel processingParallel processing

Computers MIU

Computer processing Computer processing speedsspeeds

The execution of an instruction The execution of an instruction may be measured in

Millisecond : 1/10Millisecond : 1/103 3 of a secondof a second very slow (old) computer

Microsecond : 1/10Microsecond : 1/106 6 of a secondof a second Nanosecond : 1/10Nanosecond : 1/109 9 of a secondof a second

modern computer Picosecond : 1/10Picosecond : 1/1012 12 of a secondof a second

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Computer processing Computer processing speedsspeeds

Microprocessor speedsMicroprocessor speedsare determined by are determined by MicroprocessorMicroprocessor’’s clock speeds clock speed MIPSMIPS MegaflopMegaflop

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MicroprocessorMicroprocessor’’s clock s clock speedspeed

Usually expressed in Usually expressed in megahertz (MHz) megahertz (MHz)

106 of machine cycles per second gigahertz (GHz) gigahertz (GHz)

109 of machine cycles per second Ex. a PC listed at 500MHzEx. a PC listed at 500MHz

: capable of handling 500*106 machine cycles/s

Direct comparison of clock speedsDirect comparison of clock speeds Meaningful only between identical Meaningful only between identical

microprocessorsmicroprocessors

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MIPSMIPS

One One mmillion illion iinstructions nstructions pper er ssecondecond Ex. A computer with speed of 0.5MIPSEx. A computer with speed of 0.5MIPS

: execute 500,000 instructions per : execute 500,000 instructions per secondsecond

High-speed personal computer High-speed personal computer

: perform at 100 MIPS and higher.: perform at 100 MIPS and higher. A more accurate measure than clock A more accurate measure than clock

speedspeed

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MegaflopMegaflop

One One mmillion illion flofloating-ating-ppoint operation per oint operation per secondsecond

The ability of the computer to perform The ability of the computer to perform complex mathematical operation.complex mathematical operation.

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CacheCache

Temporary storage areaTemporary storage area Designed to speed up data transfer Designed to speed up data transfer

within the computerwithin the computer Types Types

Memory cacheMemory cache Disk cache ; chapter 6Disk cache ; chapter 6

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Memory cacheMemory cache

A relatively small block of very fast A relatively small block of very fast memorymemory Designed for the specific purpose of Designed for the specific purpose of speeding speeding

upup the internal transfer of data and software the internal transfer of data and software instructions.instructions.

The data and instructions stored in cache The data and instructions stored in cache

: are : are most recently or most frequently used.most recently or most frequently used. Types Types

Internal cacheInternal cache External cacheExternal cache

Computers MIU

Memory cacheMemory cache

Computers MIU

Memory cacheMemory cache

Internal cache, Level 1 (L1) cacheInternal cache, Level 1 (L1) cache In the processorIn the processor The fastest sortThe fastest sort Takes up precious space and increase the cost of Takes up precious space and increase the cost of

the microprocessorthe microprocessor No more than 128KB No more than 128KB

External cache, Level 2 (L2) cacheExternal cache, Level 2 (L2) cache On separate chipsOn separate chips Probably 256KB or 512KBProbably 256KB or 512KB SRAM technologySRAM technology Cheaper and slower than L1 cacheCheaper and slower than L1 cache much faster (and more expensive) than much faster (and more expensive) than

memorymemory

Computers MIU

Flash MemoryFlash Memory

Memory : volatileMemory : volatile

Secondary storage : slow rateSecondary storage : slow rate Flash memoryFlash memory

nonvolatile RAMnonvolatile RAM Faster than secondary storageFaster than secondary storage

Used in cellular phones, digital cameras, and digital music recorders

Replacing disks in some handheld computers Being produced in credit card Smaller than a disk drive Require only half the power

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RISC TechnologyRISC Technology

Instruction setInstruction set a specific group of instructions a specific group of instructions that each type of that each type of

CPU is designed to understand CPU is designed to understand such as ADD or MOVE

A single program instructionA single program instruction May be made up of a substantial number of subinstructions,

each of which must take at least one machine cycle

Instructions set computing typesInstructions set computing types CISC (CISC (Complex instruction set computingComplex instruction set computing)) RISC (RISC (Reduced instruction set computingReduced instruction set computing))

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RISC TechnologyRISC Technology

CISC (CISC (Complex instruction set computing)Complex instruction set computing) Many of the most complex instructions in the Many of the most complex instructions in the

instruction set are rarely usedinstruction set are rarely used A problem to speedy performance

IntelIntel’’s Pentium familys Pentium family RISC (RISC (Reduced instruction set computing)Reduced instruction set computing)

Small subset of instructionsSmall subset of instructions Increase the speedIncrease the speed Programs in graphics and engineering areasPrograms in graphics and engineering areas

A significant performance advantage PowerPCs and AlphasPowerPCs and Alphas

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Parallel ProcessingParallel Processing

Serial processingSerial processing The execution of one instruction at a timeThe execution of one instruction at a time

Pipelining Pipelining An instruction action doesnAn instruction action doesn’’t need to be t need to be

completed before the next instruction completed before the next instruction action is begun.action is begun.

An instruction : One fetch is complete for it and it moves to decode.

the next instruction : Fetch is begun for the next.

Problem : a single electronic pathway (bus Problem : a single electronic pathway (bus line) acts like a bottle neck.line) acts like a bottle neck.

Computers MIU

Computers MIU

Parallel ProcessingParallel Processing

A method of using multiple processors at A method of using multiple processors at the same timethe same time Many processor, each with its own memory Many processor, each with its own memory

unit, working at the same timeunit, working at the same time Ultimate speed solutionUltimate speed solution Capable of operating in term of teraflopsCapable of operating in term of teraflops

Trillions of floating-point instruction per Trillions of floating-point instruction per secondsecond Network server : with 4 to 16 processors Supercomputer : with 100 or 1000 processors