Chapter1
- 1. Computer System Overview Chapter 1
- 2. Operating System Exploits the hardware resources of one or more processors Provides a set of services to system users Manages secondary memory and I/O devices
- 3. Computer Components CPU - It is basically the brain of your computer. The CPU is a used to process everything from basic to complex functions in a computer.
- 4. Computer Components RAM - RAM is memory that attaches to the motherboard. RAM is hardware used to temporarily store and access data..
- 5. Computer Components Motherboard - A Motherboard is the most important component in a computer system. All of the other hardware in a computer system connect to the motherboard.
- 6. Computer Components Power Supply - A Power Supply is the sends power to all of the other hardware so they can operate.
- 7. Computer Components Hard Drive - A Hard Drive is used for permanently storing files and programs.
- 8. Computer Components Disk Drives - Disk Drives can be a floppy drive, CD drive, DVD drive or other possible file storage devices that are used in a computer.
- 10. Basic Elements Processor Main Memory volatile referred to as real memory or primary memory I/O modules secondary memory devices communications equipment terminals System bus communication among processors, memory, and I/O modules
- 11. Processor Two internal registers ( When the processor executes instructions, data is temporarily stored in small, local memory locations of 8, 16, 32 or 64 bits called registers .) Memory address register (MAR) Specifies the address for the next read or write Memory buffer register (MBR) Contains data written into memory or receives data read from memory I/O address register I/O buffer register
- 13. Processor Registers User-visible registers Enable programmer to minimize main-memory references by optimizing register use Control and status registers Used by processor to control operating of the processor Used by privileged operating-system routines to control the execution of programs
- 14. User-Visible Registers May be referenced by machine language Available to all programs - application programs and system programs Types of registers Data Address Index Segment pointer Stack pointer
- 15. User-Visible Registers Address Registers Index Involves adding an index to a base value to get an address Segment pointer When memory is divided into segments, memory is referenced by a segment and an offset Stack pointer Points to top of stack
- 16. Control and Status Registers Program Counter (PC) Contains the address of an instruction to be fetched Instruction Register (IR) Contains the instruction most recently fetched Program Status Word (PSW) Condition codes Interrupt enable/disable Supervisor/user mode
- 17. Control and Status Registers Condition Codes or Flags Bits set by the processor hardware as a result of operations Examples Positive result Negative result Zero Overflow
- 18. Instruction Execution Two steps Processor reads instructions from memory Fetches Processor executes each instruction
- 20. Instruction Fetch and Execute The processor fetches the instruction from memory Program counter (PC) holds address of the instruction to be fetched next Program counter is incremented after each fetch
- 21. Instruction Register Fetched instruction is placed in the instruction register Categories Processor-memory Transfer data between processor and memory Processor-I/O Data transferred to or from a peripheral device Data processing Arithmetic or logic operation on data Control Alter sequence of execution
- 22. Characteristics of a Hypothetical Machine
- 23. Example of Program Execution
- 24. Direct Memory Access (DMA) I/O exchanges occur directly with memory Processor grants I/O module authority to read from or write to memory Relieves the processor responsibility for the exchange
- 25. Interrupts Interrupt the normal sequencing of the processor Most I/O devices are slower than the processor Processor must pause to wait for device
- 27. Program Flow of Control Without Interrupts
- 28. Program Flow of Control With Interrupts, Short I/O Wait
- 29. Program Flow of Control With Interrupts; Long I/O Wait
- 30. Interrupt Handler Program to service a particular I/O device Generally part of the operating system
- 31. Interrupts Suspends the normal sequence of execution
- 32. Interrupt Cycle
- 33. Interrupt Cycle Processor checks for interrupts If no interrupts fetch the next instruction for the current program If an interrupt is pending, suspend execution of the current program, and execute the interrupt-handler routine
- 34. Timing Diagram Based on Short I/O Wait
- 35. Timing Diagram Based on Short I/O Wait
- 37. Changes in Memory and Registers for an Interrupt
- 38. Changes in Memory and Registers for an Interrupt
- 39. Multiple Interrupts Disable interrupts while an interrupt is being processed
- 40. Multiple Interrupts Define priorities for interrupts
- 42. Multiprogramming Processor has more than one program to execute The sequence the programs are executed depend on their relative priority and whether they are waiting for I/O After an interrupt handler completes, control may not return to the program that was executing at the time of the interrupt
- 43. Memory Hierarchy Faster access time, greater cost per bit Greater capacity, smaller cost per bit Greater capacity, slower access speed
- 44. Memory Hierarchy
- 45. Going Down the Hierarchy Decreasing cost per bit Increasing capacity Increasing access time Decreasing frequency of access of the memory by the processor Locality of reference
- 46. Secondary Memory Nonvolatile Auxiliary memory Used to store program and data files
- 47. Disk Cache A portion of main memory used as a buffer to temporarily to hold data for the disk Disk writes are clustered Some data written out may be referenced again. The data are retrieved rapidly from the software cache instead of slowly from disk
- 48. Cache Memory Invisible to operating system Increase the speed of memory Processor speed is faster than memory speed Exploit the principle of locality
- 49. Cache Memory
- 50. Cache Memory Contains a copy of a portion of main memory Processor first checks cache If not found in cache, the block of memory containing the needed information is moved to the cache and delivered to the processor
- 53. Cache Design Cache size Small caches have a significant impact on performance Block size The unit of data exchanged between cache and main memory Larger block size more hits until probability of using newly fetched data becomes less than the probability of reusing data that have to be moved out of cache
- 54. Cache Design Mapping function Determines which cache location the block will occupy Replacement algorithm Determines which block to replace Least-Recently-Used (LRU) algorithm
- 55. Cache Design Write policy When the memory write operation takes place Can occur every time block is updated Can occur only when block is replaced Minimizes memory write operations Leaves main memory in an obsolete state
- 56. Programmed I/O I/O module performs the action, not the processor Sets appropriate bits in the I/O status register No interrupts occur Processor checks status until operation is complete
- 57. Interrupt-Driven I/O Processor is interrupted when I/O module ready to exchange data Processor saves context of program executing and begins executing interrupt-handler No needless waiting Consumes a lot of processor time because every word read or written passes through the processor
- 58. Direct Memory Access Transfers a block of data directly to or from memory An interrupt is sent when the transfer is complete Processor continues with other work