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CS240 Sequence 1

Introduction, Processors, Instruction and program execution, DMA, Interrupts, Mu

QuestionAnswer
What is the function of an 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
What are the Basic Elements of an Operating System? >Processor >Main Memory >I/O modules >System bus
How stable is main memory? very volatile
What else is main memory referred too as? > real memory > primary memory
What are I/O modules? >secondary memory devices >communications equipment >terminals
What is a System bus ? communication among processors, memory, and I/O modules
What registers are contained in a Processor ? >I/O address register >I/O buffer register >Internal Registers
What are Internal Registers? >Memory address register (MAR) >Memory buffer register (MBR)
What is a Memory address register (MAR)? Specifies the address for the next read or write
What is a Memory buffer register (MBR)? Contains data written into memory or receives data read from memory
What are the types of Processor Registers ? >User-visible registers >Control and status registers
What are User Visible Registers? Enable programmer to minimize main- memory references by optimizing register use
What are 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
What are User-Visible Registers referenced by? machine language
What is the availability of User-Visible Registers? Available to all programs >application programs >system programs
What are the types of User-Visible Registers? >Data >Address
What is contained in an Address Register? >Index >Segment pointer >Stack pointer
What is an index ? involves adding an index to a base value to get an address
What is a Segment Pointer? When memory is divided into segments, memory is referenced by a segment and an offset
What is a Stack Pointer? Points to top of stack
What are the types of Control and Status Registers ? >Program Counter (PC) >Instruction Register (IR) >Program Status Word (PSW)
What is a Program Counter (PC)? Contains the address of an instruction to be fetched
What is a Instruction Register (IR) ? Contains the instruction most recently fetched
What are Program Status Word (PSW)? >Condition codes >Interrupt enable/disable >Supervisor/user mode
What are Condition Codes or Flags? Bits set by the processor hardware as a result of operations
What are some examples of Condition Codes? Condition Flags? >Positive result >Negative result >Zero >Overflow
What are the steps of Instruction Execution? >Processor reads instructions from memory >Processor executes each instruction
How many steps are in Instruction Execution? two
What is the term for when the processor reads instructions from memory? fetches
Describe the Program counter role in Instruction Fetch and Execution >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
Where is the fetched instruction placed? in the instruction register
What are the categories of instruction registers? >Processor-memory >Processor-I/O >Data processing >Control
What is the Processor-memory instruction register for? transfers data between processor and memory
What is the Processor-I/O instruction register for? data transferred to or from a peripheral device
What is data processing ? arithmetic or logical operation on data
What is control instruction register used for? alter sequence of execution
What is DMA an acronym for? Direct Memory Access
What is a 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
What is an Interrupt? Interrupt the normal sequencing of the processor
What is generally slower than the processor? I/O devices
Why are I/O devices slower than the processor? Processor must pause to wait for device
What are classes of interrupts? >Program >Timer >I/O >Hardware Failure
What is a Program Interrupt? Generated by some condition that occurs as a result of an instruction execution
What are some examples of program interrupts? >arithmetic overflow >division by zero >attempt to execute an illegal machine instruction >reference outside of a users allowed memory space
What is a Timer Interrupt? Generated by a timer within the processor. Allows for Operating System to preform certain functions on a regular basis
What is an I/O Interrupt? Generated by an I/O controller, to signal normal completion of an operation or to signal a variety of error conditions
What is a hardware failure interrupt? generated by a failure, such as power failure or memory parity error
What is an interrupt handler? Program to service a particular I/O device
What is the interrupt handler apart of? generally operating system
what do interrupts do? Suspends the normal sequence of execution
Explain the 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
What is the hardware part of the simple interrupt processing cycle? >device.controller/system.hardware.issues.an.interrupt >processor.finish.execution.current.instruction >processor.signals.acknowledgement.of.interrupt >processor.pushes.psw.pc.onto.control.stack >processor.load.new.pc.value.based.on.interrupt
What is the software part of the simple interrupt processing cycle? >save remainder of process state information >process interrupt >restore process state information >restore old psw and pc
What are the ways to apply multiple interrupts? >Disable interrupts while an interrupt is being processed >Define priorities for interrupts (interrupt within an interrupt)
What is multi-programing? Processor has more than one program to execute
How are programs executed in multi-programing? sequence is dependent on relative priority and whether they are waiting an I/O
What happens after an interrupt handler is finished executing during multi-programing? control may not return to the program that was executing at the time of the interrupt
In regards to the memory hierarchy faster access time relates to cost in what way? greater cost per bit
In regards to the memory hierarchy greater capacity relates to cost in what way? smaller cost per bit
In regards to the memory hierarchy greater capacity is related to access speed in what way? slower access speed
What is considered inboard memory? >registers >cache >main memory
what is considered outboard storage? >Magnetic Disk >CD ROM >CD RW >DVD- RIV >DVD RAM
what is considered off line storage? >Magnetic Tape >MO >Worm
List the elements of the memory hierarchy from top to bottom 1Registers 2Cache 3MainMemory 4Magnetic Disk 5Magnetic Tape
List the memory types in the hierarchy from top to bottom >inboard memory >outboard memory >offline storage
What happens as you go down the memory hierarchy? >decreasing cost per bit >increasing capacity >increasing access time >decreasing frequency of access of memory by the processor
How reliable is secondary memory? nonvolatile
what is secondary memory refereed too as? Auxiliary memory
What is secondary memory used for? Used to store program and data files
What is a disk cache? A portion of main memory used as a buffer to temporarily to hold data for the disk
what are disk writes? clustered
What is cache memory not visible too? operating system
what does cache memory do? increase the speed of memory
what is faster than memory speed? processor speed
what does cache memory exploit? principle of locality
what does cache memory contain? a copy of a portion of main memory
what does the processor check first? cache
what happens if the data the processor is looking for is not found in cache? the block of memory containing the needed information is moved to the cache and delivered to the processor
what are the elements involved in cache design ? >Cache size >Block size >Mapping function >Replacement algorithm >Write policy
What is the significance of cache size? Small caches have a significant impact on performance
What is a block size? The unit of data exchanged between cache and main memory
What is a mapping function? Determines which cache location the block will occupy
What is the Replacement algorithm ? Determines which block to replace
What is an example of a Replacement algorithm? Least-Recently-Used (LRU) algorithm
When does write policy occur? when the memory write operation takes place
How can the write policy occur? >every time block is updated >only when block is replaced
what are the key features of using a write policy where it only happens when block is replaced >Minimizes memory write operations >Leaves main memory in an obsolete state
Explain Programed 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
what is the term for when the Processor checks status until operation is complete polling
Explain 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
What are the advantages of Interrupt Driven I/O no needless waiting
What are the disadvantages of Interrupt Driven I/O consumes a lot of processor time because every word read or written passes through the processor
Explain 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
Created by: ToriOverholtzer