carl hamacher(chapter 2 )

Question

in the underline statement it is given that higher performance can be achieved if each instruction occupy one word???how it is true??what happen when two instruction occupy in single word???

Comments

BASANT KUMAR

 This is my try.. if you find any flaw please tell..

If two instructions are there in one word then in word addressable memory, after fetching two instructions ( i.e. one word) at a time we can't proceed for the next stages (Decode,Execute...) for both together. When Decode operation is carried out on one of the two fetched instructions, Fetch will be performed for the next word in the memory. Then the instruction for whom the Decode has not been performed yet would get overwritten  by the newly fetched one.

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yes you are true but is their any effect on efficiency????

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I guess if this implementation is creating such major problem then there is no advantage using it..so efficiency even if increased in terms of less no. of fetching will cause serious problem..

Answer 1

Every instructions of one word will ensure the uniformity among all the instructions and it will make easier for cpu to process every instructions i.e. if suppose only one word is accessed in one cycle and every instruction is of 1 word long then it ensures an instruction is completely executed in one cycle . So there won't be any amiguity in calculating cpu performance hence uniformity makes it easier for CPU to perform at its best