ch08 - Chapter 8: Main Memory Silberschatz, Galvin and...

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Silberschatz, Galvin and Gagne ©2009 Chapter 8: Main Memory
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8.2 Silberschatz, Galvin and Gagne ©2009 Chapter 8: Memory Management Background Swapping Contiguous Memory Allocation Paging Structure of the Page Table Segmentation Example: The Intel Pentium
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8.3 Silberschatz, Galvin and Gagne ©2009 Objectives To provide a detailed description of various ways of organizing memory hardware To discuss various memory-management techniques, including paging and segmentation To provide a detailed description of the Intel Pentium, which supports both pure segmentation and segmentation with paging
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8.4 Silberschatz, Galvin and Gagne ©2009 Background Program must be brought (from disk) into memory and placed within a process for it to be run Main memory and registers are only storage CPU can access directly Register access in one CPU clock (or less) Main memory can take many cycles Cache sits between main memory and CPU registers Protection of memory required to ensure correct operation
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8.5 Silberschatz, Galvin and Gagne ©2009 Base and Limit Registers A pair of base and limit registers define the logical address space
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8.6 Silberschatz, Galvin and Gagne ©2009 Binding of Instructions and Data to Memory Address binding of instructions and data to memory addresses can happen at three different stages Compile time : If memory location known a priori, absolute code can be generated; must recompile code if starting location changes Load time : Must generate relocatable code if memory location is not known at compile time Execution time : Binding delayed until run time if the process can be moved during its execution from one memory segment to another. Need hardware support for address maps (e.g., base and limit registers)
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8.7 Silberschatz, Galvin and Gagne ©2009 Multistep Processing of a User Program
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8.8 Silberschatz, Galvin and Gagne ©2009 Logical vs. Physical Address Space The concept of a logical address space that is bound to a separate physical address space is central to proper memory management Logical address – generated by the CPU; also referred to as virtual address Physical address – address seen by the memory unit Logical and physical addresses are the same in compile-time and load-time address-binding schemes; logical (virtual) and physical addresses differ in execution-time address-binding scheme
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8.9 Silberschatz, Galvin and Gagne ©2009 Memory-Management Unit ( MMU ) Hardware device that maps virtual to physical address In MMU scheme, the value in the relocation register is added to every address generated by a user process at the time it is sent to memory The user program deals with logical addresses; it never sees the real physical addresses
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8.10 Silberschatz, Galvin and Gagne ©2009 Dynamic relocation using a relocation register
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8.11 Silberschatz, Galvin and Gagne ©2009 Dynamic Loading Routine is not loaded until it is called
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ch08 - Chapter 8: Main Memory Silberschatz, Galvin and...

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