Consider the case where a program consists of 30% integer instructions, 50% floa
ID: 3583341 • Letter: C
Question
Consider the case where a program consists of 30% integer instructions, 50% floating-point instructions and 20% memory access operations and executes 46 billion instructions. Let a machine take 257 ps to execute an integer instruction, 683 ps to execute a floating-point instruction and 9 ns to complete a memory access operation. Assume that we can overclock the processor arbitrarily, thus speeding up the integer and floating-point performance by an arbitrary factor. What is the fastest we could finish computing this program just by overclocking the processor?
Explanation / Answer
integer instructions 30% of total instructions is (46 billion*30)/100= 13.8 billion
machine take 257 ps for each integer instruction to execute = 0.257 ns
for 13.8 billion integer instructions time require = 13.8 billion * .257 = 3.54 billion nano seconds = 3.54 sec
floating point instructions 50 % of total is ( 46 billion * 50 )/100 =23 billion
machine take 683 ps for each floating point instruction to execute = 0.683 ns
for 23 billion floating point instructions time require = 23 billion * 0.683= 15.7 billion nano seconds = 15.7 seconds
memory access instructons 20 % of total is (46 billion * 20)/100= 10.2 billion
and each memory access instruction takes 9ns
10.2 billion memory access instructions takes 10.2 * 9 ns = 91.8 billion ns = 91.8 sec
for whole program to complete time require is (3.54 + 15.7 +91.8 )sec =111.04 sec
Overclocking is the task of increasing a cpu’s clock rate, running it at a higher speed than it was designed to run.
but over clocking can improve the risk of heat produced , in our case if we over clock CPU ,
over clocking improves speed by assume 1.5 ghz (1.5 billion instructions per second ) is processor speed then by over clocking it improves 0.5 billion instructions per second speed .
for 46 billion instructions to complete it require (46 * 2 )/1.5 = 61 sec means within half of the time it completes
but it depends on processor speed and factor of over clocking.