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Memory Design Example

Memory Design Example. Selecting Memory Chip. Selecting SRAM Memory Chip. SRAM Memory Chips. SRAM Memory Chip - 1K X 4 . 1K X 4 SRAM (Part Number 2114N). 1K X 4 SRAM (Part Number 2114N). 1K X 4 SRAM (Part Number 2114N). Memory Design – 1K x 4. A[00:09] .   D[03:00].

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Memory Design Example

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  1. Memory Design Example

  2. Selecting Memory Chip

  3. Selecting SRAM Memory Chip

  4. SRAM Memory Chips

  5. SRAM Memory Chip - 1K X 4

  6. 1K X 4 SRAM (Part Number 2114N)

  7. 1K X 4 SRAM (Part Number 2114N)

  8. 1K X 4 SRAM (Part Number 2114N)

  9. Memory Design – 1K x 4 A[00:09]    D[03:00] Addr Block Select 

  10. Memory Design – 1K x 8 D[07:04] D[03:00] A[00:09]  A[00:09]    D[07:04]   D[03:00] Addr BlockSelect => Addr Block Select =>

  11. Memory Design - 2k x 8 D[07:04] D[03:00] Block x..x1y…y Block x..x0y…y

  12. D[07:04] D[03:00] Memory Design - 4k x 8 Block x..x11y…y Block x..x10y…y Block x..x01y…y Block x..x00y…y

  13. Chapter 8Operating System Support HW: 8.8, 15, 17 (Due 11/13)

  14. Objectives of Operating System • Convenience • Making the computer easier to use • Efficiency • Allowing better use of computer resources • Functions: • Managing Resources • Scheduling Processes (or tasks) • Managing Memory

  15. Layers and Views of a Computer System

  16. Operating System Services include • Program creation • Program execution • Access to I/O devices • Controlled access to files • System access • Error detection and response • Accounting

  17. O/S as a Resource Manager

  18. Types of Operating System • Interactive • Batch • Single program (Uni-programming) • Multi-programming (Multi-tasking)

  19. Simple Batch Systems • Resident Monitor program • Users submit jobs to operator • Operator batches jobs • Monitor controls sequence of events to process batch • When one job is finished, control returns to Monitor which reads next job • Monitor handles scheduling

  20. Memory Layout for Resident Monitor

  21. Job Control Language • Instructions to Monitor • Usually denoted by $ • e.g. • $JOB • $FTN • ... High Level Language Program (Fortran, COBOL, . . . ) • $LOAD • $RUN • ... Application Data for program • $END

  22. Desirable Hardware Features • Memory protection • To protect the Monitor • Timer • To prevent a job monopolizing the system • Privileged instructions • Only executed by Monitor • e.g. I/O • Interrupts • Allows for relinquishing and regaining control

  23. Multi-programmed Batch Systems • I/O devices are very slow  Waiting is inefficient use of computer • When one program is waiting for I/O, another can use the CPU

  24. Uni-programmed System

  25. Multi-Programming with Three Programs

  26. Sample Program Mix

  27. Utilization: Uni-programmed vs Multi-programmed

  28. Multiprogramming Resource Utilization

  29. Some Types of Systems • Uniprogramming - One user at a time uses the computer • Time Sharing - Allow users to interact directly with the computer • i.e. Interactive • Multi-programming - Allows a number of users to interact with the computer

  30. Types of Scheduling

  31. Five State Process Model

  32. Process Control Block

  33. Scheduling Sequence Example

  34. Key Elements of O/S

  35. Process Scheduling

  36. Memory Management • Uni-programming • Memory split into two • One for Operating System (monitor) • One for currently executing program • Multi-programming • “User” part is sub-divided and shared among active processes • Note: Memory size -16 bits  64K memory addresses - 24 bits  16M memory addresses - 32 bits  4G memory addresses

  37. Swapping • Problem: I/O is so slow compared with CPU that even in multi-programming system, CPU can be idle most of the time • Solutions: • Increase main memory • Expensive • Swapping

  38. What is Swapping? • Long term queue of processes stored on disk • Processes “swapped” in as space becomes available • As a process completes it is moved out of main memory • If none of the processes in memory are ready (i.e. all I/O blocked) • Swap out a blocked process to intermediate queue • Swap in a ready process or a new process • But swapping is an I/O process… • Isn’t I/O slow? • So why does swapping make sense ?

  39. Use of Swapping

  40. Partitioning • Partitioning: May not be equal size Splitting memory into sections to allocate to processes (including Operating System!) • Fixed-sized partitions • Potentially a lot of wasted memory • Variable-sized partitions • Process is fitted into smallest hole that it will fit in • Dynamic partitions • no room for additional memory allocation • memory leak – need periodic coalescing, or – need periodic compaction

  41. Fixed Partitioning

  42. Effect of Dynamic Partitioning

  43. Relocation Challenges • Can’t expect that process will load into the same place in memory • Instructions contain addresses • Locations of data • Addresses for instructions (branching) • Logical address - relative to beginning of program • Physical address - actual location in memory (this time) Solution: • Use Base Address & Automatic (hardware) conversion

  44. Paging • Split memory into equal sized, small chunks -page frames • Operating System maintains list of free frames • Split programs (processes) into equal sized small chunks - pages • Allocate the required number page frames to a process - A process does not require contiguous page frames - Each process has its page table

  45. Allocation of Free Frames

  46. Logical and Physical Addresses - Paging

  47. Virtual Memory • Demand paging • Do not require all pages of a process in memory • Bring in pages as required • Page fault • Required page is not in memory • Operating System must swap in required page • May need to swap out a page to make space • Perhaps select page to throw out based on recent history

  48. Thrashing • Too many processes in too little memory • Operating System spends all its time swapping • Little or no real work is done • Solutions • Good page replacement algorithms • Reduce number of processes running • Add more memory

  49. Virtual Memory • We do not need all of a process in memory for it to run - We can swap in pages as required • So - we can now run processes that are bigger than total memory available! • Main memory is called real memory • User/programmer can see much bigger memory space - virtual memory

  50. Inverted Page Table Structure

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