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23 Cards in this Set
- Front
- Back
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What is the main advantage of polling? |
No overhead caused by interrupt. |
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What is the main disadvantage of polling? |
Loops consume a lot of CPU time. |
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What is a well-suited application for polling? |
Output to a printer (character by character). |
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What is the main advantage of interrupts? |
Until one occurs, CPU is free to execute other code. |
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What is the main disadvantage of interrupts? |
Fast machines would spend all their time doing i/o when transferring data. |
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What is a well-suited application for interrupts? |
Input a character from a keyboard. |
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What is the main advantage of direct memory access? |
No CPU intervention, high transfer rates, few CPU cycles per transfer. |
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What is the main disadvantage of direct memory access? |
Requires a DMA controller out carry out a transfer operation. |
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What is the best suited application for direct memory access? |
Inputting a block of data from a hard disk. |
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Give an example of a program structure that exhibits good spatial locality. |
Any kind of linearly sequential data structure. |
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Give an example of a program structure that exhibits good temporal locality. |
Any kind of merging loop that touches the same data several times. |
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What characteristic of the memory hierarchy does cache memory improve? |
Cache memory improves the access speed to data stored in memory. |
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How does cache memory rely on the principle of locality? |
Cache memory relies on the principle of locality to determine which data objects should be stored in the cache, in order to optimize the likelihood that they will be referenced. |
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Explain how demand paged virtual memory provides a performance improvement because of the principle of locality exhibited by programs. |
Demand paged virtual memory uses temporal locality to create a working set of pages in memory, allowing for dynamic memory allocation. |
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How does demand paged virtual memory give application programs the illusion of more main memory than physically exists in the program? |
The operating system only copies a disk page into physical memory if an attempt is made to access it and that page is not already in memory |
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A page fault is caused by: |
A CPU reference made to a word in virtual memory that is not cached in DRAM. |
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Describe the steps taken when a page fault occurs (3). |
1) Interrupt page, 2) determine least recently used in page table, 3) swap requested page with LRU. |
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Give the two types of "exceptions" in a typical computer system: |
1) Processor detected exceptions, 2) programmed exceptions. |
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List the steps taken by the computer when a hardware interrupt occurs. |
1) Finish execution of current instruction, 2) disable further interrupts, 3) save current program state, 4) initiate interrupt service routine, 5) restore saved state, 6) return to interrupted program. |
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The TLB is a _______ of recently used page entries. |
Small cache. |
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The TLB is located in the _______. |
Memory Management Unit. |
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If the TLB didn't exist in a demand paged virtual memory system, every main memory reference would require two main memory access: 1) ________ and 2) ________ |
1) to access the page table, 2) to access the physically address stored in the page table |
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Yay |
Okay |
