Main Memory of Computer

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Main Memory of Computer. Learning Objectives. To realize: 1.The needs of computer memory 2.Memory sizes of computer 3.Types of memory 4.Main memory. Introduction to computer memory. Comparison between human and computer memory. Role Play: - PowerPoint PPT Presentation

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Main Memory of ComputerLearning ObjectivesTo realize:1.The needs of computer memory2.Memory sizes of computer3.Types of memory4.Main memoryIntroduction to computer memoryComparison between human andcomputer memoryRole Play:If you can now choose your brain memory, what would you choose:1)Large storage with low speed2)Small storage with high speed3)Large storage with high speed$300$500$1000Basic Memory UnitsBinary representation is used to represent all data and instructions in computer8bits = 1byte = word symbol1KB(Kilobyte) = 1024B1MB(Megabyte) = 1024KB1GB(Gigabyte) = 1024MBMemory Sizes The size of the main memory is measured in kilobytes (KB),which is equal to 1024 bytes. For convenience,we sometimes round off the value of K to 1000.For example,640 KB is approximately 640 000 bytes (640 x 1000).To measure memory of large sizes,we use megabytes (MB) and gigabytes (GB).1 MB = 1024 KB = 220 bytes ~ 1 million bytes1 GB = 1024 MB = 230 bytes ~ 1 billion bytesQuizQ1: 64MB = ? BytesQ2: 2GB = ? BitsClassification of MemoryMain MemoryBacking Storage DevicesCache MemoryHow Main Memory works with CPU ?000000010010 READ A0011 READ B010000100010READ AREAD A+1MARMDRMain MemoryRAM: Random Access MemoryROM: Read Only MemoryROM (top) and RAM (bottom) on a motherboard (right)RAM1.Data can be read from any word or written onto any word in the RAM.2.When a program is run,the instructions and the working data are temporarily stored in the RAM.3.When the computer is switched off,all the data held in the RAM are lost.RAM is therefore volatile.Different types of RAMThere are two basic types of RAM, dynamic RAM and static RAM. DRAMDRAM (Dynamic RAM) is a type of memory that must be re-energizedconstantly or its contents will be lost.1.SDRAM (Synchronous DRAM) is a fasterversion of DRAM becauseit is synchronized to the system clock.2.RDRAM (Rambus DRAM) is a newer type of DRAM that is even faster than SDRAM. SRAMSRAM (Static RAM) is faster and more reliable than any form of DRAM,but are more expensive.SRAM does not have to be re-energized as often as DRAM. Comparison between DRAM and SRAMLike a rechargeable batteryEvery read, discharging the battery, need to recharge.Even you do not read, it will discharge!Need to recharge periodically.Slow.Use in motherboardLike a light bulbNo dischargingRelatively FastUse in CPU, as registerDRAMSRAMROM1.Data can only be read from the ROM.The contents cannot be overwritten.2.ROM is used by the computer manufacturer to store the systems programs.These programs control the fundamental operations.3.ROM is non-volatile.When the power is switched off,the contents of the ROM remain unaffected.Different types of ROM1. A programmable read-only memory (PROM) 2. Flash memory or Flash ROMSummary on different types of computer memory~ The End ~

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