410exam1cheatsheet

# 410exam1cheatsheet - Spatial Locality a[1 a[2 a[3 temporal...

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Spatial Locality : a[1] a[2] a[3] temporal locality: a[0] If referenced word is in the cache, 20ns are required. If is in main memory but not in the cache, 60 ns are needed to load into cache. If the word is not in main memory, 12ns are required to fetch from disk, follow by 60ns to copy to cache. The cache hit ratio is 0.9 and the main memory hit ratio is 0.6, what is the average time to access a reference? (20*0.9)+((20+60)*0.1*0.6)+((12+60+20)*0.1*.04) = 26.48 Why DMA access to main memory is given higher priority than processor? Processor will only be interrupted accessing a single unit of data. If the DMA is interrupted, a larger block of data will be affected. Tc =100ns Tm =1200ns Cc =0.01cent/bit Cm =0.001cent/bit What is the cost of 1 MByte of main memory? 1.024*10^6*0.001/100 = 81.92 What is the cost of 1 MByte of main memory using cache memory technology? ? 1.024*10^6*0.01/100 = 819.2 If effective access time is 10% greater than the cache access time, what is the hit ratio H? 110/100 TC =H*Tc+(1-H)(Tc+Tm) H=1190/1200 What are the operating system and three objective of design? Control the execution of a application program, a interface between application and hardware. Convenience, efficiency, and ability to evolve. Kernel of an OS? Portion of operating system that is in the main memory. Multiprogramming? When one job needs to wait for I/O, the processor can switch to the other job. In 1one computation period, T for a job, half the time is spending in I/O and the other half in processor. Each job runs for a total of N periods. Period is distributed as I/O first half and processor second half. One two four Turnaround time N*T N*T 2N*T Throughput 1/N 2/N 2/N Processor 50% 100% 100% 0001 = Load AC from memory 0010 = Store AC to memory 0101 = Add to AC from memory MAR: 300 301 301 302 302 302 MBR: 0 3 3 2 2 5 What is processor? A program in execution.

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