A certain microprocessor requires either 2, 3, 4, 8, or 12 machine cycles to per

Question

A certain microprocessor requires either 2, 3, 4, 8, or 12 machine cycles to perform various operations. 25 percent of its instructions require 2 machine cycles, 20 percent require 3 machine cycles, 17.5 percent require 4 machine cycles, 12.5 percent require 8 machine cycles, and 25 percent require 12 machine cycles. A) What is the average number of cycles per instruction for this microprocessor? B) What is the clock rate (machine cycles per second) required for this microprocessor to be a "1 MIPS" processor? C) Suppose this system requires an extra 20 machine cycles to retrieve an operand from memory. It has to go to memory 40% of the time. What is the average number of machine cycles per instruction for this microprocessor including its memory fetch instructions?

Explanation / Answer

5.8 cycles/instruction. It's probability of it * number of cycles so 2*.25+3*.2+4*.175+8*.125+12*.25=5.8 5.8 MHz so we can get the 5.8 cycles per instruction * 1 million instructions per second gets us 5.8 million cycles per second (2*.25+3*.2+4*.175+8*.125+12*.25)+20*.4=13.8. I was checking my answers with a key and I see it is 13.25. If the second is right, I'll relook at it in a bit.

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