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CIS3360_HW5_Solution-3-22-10

# CIS3360_HW5_Solution-3-22-10 - Page 1 of 8 CIS 3360...

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Page 1 of 8 CIS 3360 – Security in Computing Spring 2010 Solution for Homework 5 (100 points) 1) [5] Fill the following table: 1 THz = ____10 12 ____ Hz 1 GHz = ____10 9 _____ Hz 1 MHz = ____10 6 _____ Hz 1 KHz = ____10 3 _____ Hz 1 Hz = _____1____ cycles per second 2) [5] If a frequency is given as 1 MHz, how much time in milliseconds does one cycle take? Recall that 1 milliseconds = 1ms = 10 -3 seconds. Answer: Frequency = Cycle / Second 1 MHz = 1000000/1000 cycles/ms = 1000 cycles/ms Thus 1 cycle takes 1/1000 ms = 0.001 ms 3) [10] If a data block has 512 bytes and the bus is 32 bit wide, how much time in microseconds does it take to fetch the entire data block assuming the bus operates at 1 MHz? If the bus is 64 bits wide, running at 1 MHz, how much time (in μ s) does it take? If the bus is 32-bits wide, running at 4 MHz, how much time (in μ s) does it take? Recall that 1 microseconds = 1 μ s = 10 -6 seconds. Answer: Case 1: 32-bit wide bus, running at 1 MHz First, we will find the no. of cycles it takes to transfer the 512 bytes on a 32-bit wide bus # of cycles = (512 bytes * 8 bits) / 32 bits = 4096 bits / 32 bits = 128 cycles Now, we will find the time for one cycle: The bus is running at 1 MHz. So, 1 cycle will take 1/1000 000 secs = 10 -6 s = 1 μ s. So, time for 128 cycles is: 128 x 1 μ s = 128 μ s Thus, it takes 128 microseconds to transfer entire block.

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Page 2 of 8 Case 2: 64-bit wide bus, running at 1 MHz # of cycles = (512 bytes * 8 bits) / 64 bits = 4096 bits / 64 bits = 64 cycles The bus operates 1000000 cycles in 1 second. Thus, the operation of 64 cycles, it should take (64/1000000) = 0.000064 second. 1 second = 10 6 microseconds 0.000064 second = 0.000064 x 10 6 = 64 microseconds Thus, it takes 64 microseconds to transfer entire block. Case 3: 32-bit wide bus, running at 4 MHz # of cycles = (512 bytes * 8 bits) / 32 bits = 4096 bits / 32 bits = 128 transfers The bus operates 4000000 cycles in 1 second. Thus, the operation of 128 cycles, it should take (128/4000000) = 0.000032 second. 1 second = 10 6 microseconds 0.000032 second = 0.000032 x 10 6 = 32 microseconds Thus, it takes 32 microseconds to transfer entire block. 4)
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CIS3360_HW5_Solution-3-22-10 - Page 1 of 8 CIS 3360...

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