A. Frank - P. Weisberg Operating Systems Functional View of Operating System
2 A. Frank - P. Weisberg Contents • Computer System Organization • Main Memory Management • Memory Protection • I/O Protection • CPU Protection • Types of Interrupts: 1. Traps 2. External interrupts 3. System calls
3 A. Frank - P. Weisberg Computer System Organization One or more CPUs, device controllers connect through .common bus providing access to shared memory Concurrent execution of CPUs and devices competing for .memory cycles
4 A. Frank - P. Weisberg Storage Structure • Main memory – only large storage media that the CPU can access directly. • Secondary storage – extension of main memory that provides large nonvolatile storage capacity. • Hard disks – rigid metal or glass platters covered with magnetic recording material: – Disk surface is logically divided into tracks, which are subdivided into sectors. – The disk controller determines the logical interaction between the device and the computer.
5 A. Frank - P. Weisberg Storage Hierarchy
6 A. Frank - P. Weisberg Performance of Various Levels of Storage
7 A. Frank - P. Weisberg Caching • Important principle, performed at many levels in a computer (in hardware, operating system, software). • Information in use is copied from slower to faster storage temporarily. • Faster storage (cache) checked first to determine if information is there: – If it is, information used directly from the cache (fast). – If not, data copied to cache and used there. • Cache smaller than storage being cached: – Cache management is an important design problem. – Cache size and replacement policy matter.
8 A. Frank - P. Weisberg Main Memory Management • Initial memory management techniques: 1. Minimal management – one program that manages memory for itself. No memory protection problems here. 2. Memory split – Resident Monitor and User Job/Program split the memory between them. 3. Memory Division – The operating system and a few user jobs divide the available memory between them.
9 A. Frank - P. Weisberg MS-DOS Memory Split
10 A. Frank - P. Weisberg Memory Management Dynamics • Sharing system resources requires the operating system to ensure that an incorrect program cannot cause other programs to execute incorrectly. • Resident Monitor is a “Trusted Program” but how to protect it from damage by the user program? • Solution: Fence Register (a dedicated register) and addressing access logic.
11 A. Frank - P. Weisberg Memory Split Resident Monitor User Program Fence Register 0K 64K 16K
12 A. Frank - P. Weisberg Fence Register • The Fence Register is loaded with the base of the user program (which is also the limit of the Resident Monitor).
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- Summer '18
- Virtual memory, Central processing unit, Interrupt, Interrupt handler