GATE 2019 CS – Question 55
A certain processor deploys a single-level cache. The cache block size is 8 words and the word size is 4 bytes. The memory system uses a 60-MHz clock. To service a cache miss, the memory controller first takes 1 cycle to accept the starting address of the block, it then takes 3 cycles to fetch all the eight words of the block, and finally transmits the words of the requested block at the rate of 1 word per cycle. The maximum bandwidth for the memory system when the program running on the processor issues a series of read operations is ________ $\times10^6$ bytes/sec.
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Correct answer: 160
Explanation
A miss takes $1+3+8=12$ cycles and transfers $8\times4=32$ bytes. At 60 MHz the bandwidth is $\frac{32\text{ B}}{12\text{ cycles}}\times60\times10^6=160\times10^6$ bytes/sec.