MemoryOutlineMemory HierarchyMemory CharacteristicsDefinitionSlide 6Addressing ModesBasic Addressing ModesSlide 9Slide 10Slide 11Special Addressing ModesSlide 13Slide 14Virtual MemoryMemory System ArchitectureMemory CellsMemory OrganizationSlide 19Slide 20PowerPoint PresentationSlide 22Slide 23Slide 24Slide 25Slide 26Slide 27Memory Memory Farhana RahmanDecember 7th , 2004CS147, SECTION 3OutlineOutlineMemory HierarchyAddressing ModesArchitecture Types of MemoryMemory HierarchyMemory Hierarchy Memory refers to any storage medium used for storing information. Since there are many different kinds of storage media , we can categorize them according to the memory speed.The memory hierarchy is as follows:Cache MemorySecondary memoryMain (primary) memoryArchival memoryMemory CharacteristicsMemory CharacteristicsMemory TypeCache Main Secondary ArchivalTechnology TTL MOS Magnetic PaperSpeed (access time)10^1 ns 10^2 ns 10^3 ns 10^5 nsSize(capacity)Small,< 8K Medium,64K-8MLarge,300K-1GVery large, Usage Processor,Data BufferOn-line, Dynamic,Temporary StorageOn-line,Bulk storageArchival, Off-line, permanent storageRepresentativeExampleTTLmemoriesSemiconductorMemoriesFloppy disk,Hard disk,tapePaperDefinitionDefinitionCache Memory: The cache memory is a small section of memory that is usually placed between the processor and the main memory and is used when the main memory speed is much slower than the processor speed.Main (Primary) Memory: The main memory contains the primary storage space, which is randomly accessible by the processor.The primary function of the main memory is to store the instructions and data necessary for the current execution of the processor.Secondary Memory: The information stored in the main memory is not easily accessible to the programmer and is not suited for storing a lot of information. Secondary storage media are useful for this purpose. Archival Memory: Archival memory refers to permanent storage media.This include media such as cards and paper printouts. Their use is strictly for the programmer to store computation results.DefinitionDefinitionIn order to access the memory, an address must be provided.The manner in which the address is specified in an instruction is called the addressing mode. Addressing modes can be categorized into:Basic addressing modes Special addressing modesAddressing ModesAddressing ModesBasic Addressing ModesBasic Addressing ModesMost computer systems use a number of basic addressing modes to obtain operands from memory; many high performance processors include additional addressing modes consistent with the design philosophies of the processor. Basic addressing modes include: Implied addressing Immediate addressing Register Addressing Direct Addressing Register indirect addressing Implied register indirect addressing Indexed addressingOPROPCODEMPCMDRIRImmediate addressing (microcomputers)Basic Addressing ModesBasic Addressing ModesOPCODE OPR OPCODE OPRPCImmediate addressing (large computers)IRIR OPRImplied addressing(implied)Basic Addressing ModesBasic Addressing ModesReg.# 2IRReg.# 2 (OPR)Reg.# 1Reg.# 3Reg.# 4Register addressingOPCODE ADDROPRMPCDirect addressing (large computers)OPCODEADDROPRMMARPCDirect addressing (microcomputers)Basic Addressing ModesBasic Addressing ModesReg. # 1Reg. # 2Reg. # 3OPRMOPCODE Reg. #2IRRegister indirect addressingReg. # 2OPRMOPCODEIR(implied)Implied register indirect addressingOPCODE Reg. # 2IndexReg. # 3Reg. # 2Reg. # 2OPRMIRIndexed addressingSpecial Addressing ModesSpecial Addressing ModesMany processors have additional or special addressing modes that facilitate ease implementing language constructs and primitives often used in operating systems and other systems programming environments. Special addressing modes include: Relative addressing Base addressing Page addressing Indirect addressingSpecial Addressing ModesSpecial Addressing ModesOPCODE offsetPCoffsetOPRMIRRelative addressingSpecified addressBase registerOPRMBase addressingSpecial Addressing ModesSpecial Addressing ModesPage EAOPRMPage addressingPage registerADDROPRMEAIndirect addressingIn some computer systems it is convenient for the user to be able to specify a memory space that is larger than the actual installed memory space. This is called virtual memory.The operation of a virtual memory system uses the concept of memory segmentation. The user’s entire virtual memory space is segmented into pages of segments and is stored as pages or segments in secondary memory. A page is a fixed block of memory, whereas a segment is a variable-size block of memory.Virtual MemoryVirtual MemoryMemory System ArchitectureMemory System ArchitectureThe main elements of the memory system architecture are: Memory Cells Memory Organization Bit-Slice Organization Memory Segmentation Board/Bank Segmentation Memory Access TimeMemory CellsMemory CellsThe memory cell is a simple flip-flop or a bistable multivibrator that can be found in one of two stable states: an ON state and an OFF state. Memory components are composed of three major parts: the memory cells, the row decoder, and the column decoder.Memory OrganizationMemory OrganizationMemory organization is usually given in terms of the number of individually accessible or addressable words in the chip and the word length. Bit –Slice Organization: The concept of bit-slice organization is to have many chips operating together in parallel, each responsible for the operations within a thin slice (a few bits) of the word. Memory Segmentation: Although the bit-slice organization technique provides the necessary tools for the design of a memory system with any width, the memory segmentation technique gives the necessary tools for the design of a memory system with any depth. In memory segmentation, many memory chips are connected together to form the complete memory system. Memory OrganizationMemory Organization Board/Bank Segmentation: Often only a fixed number of memory chips can fit into a specific size of circuit board. If more memory is required, multiple memory boards are used. The portion Of memory located on a particular board is called a memory bank. The total memory is composed of many memory banks. All banks are usually connected to a motherboard.Memory OrganizationMemory Organization Memory Access Time: This is an important performance parameter for memory chips.
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