Consider a change to the singlecycle processor that replaces

Consider a change to the single-cycle processor that replaces the LOAD instructions with the pair of new instructions in the following way What is the advantage of such code modification? What is the disadvantage of such code modification? Assume that the datapath components have the following delays: ALU - 2 nsec, register file read - 1 nsec, instruction memory - 2 nsec, data memory - 2 nsec. You can ignore all other delays and also assume that register file and memory write delays are not accounted for separately. Assume that LOAD instructions account for 30% of ail instructions in the program. Would this modification result in a performance improvement or degradation? Explain. For the datapath component delays as presented in part (c), determine the maximum percentage of LOAD instructions in a program, so that the proposed modification still has a positive impact on performance. Explain

Solution

a) In a single-cycle processor one instuction is carried out in a cycle. So, To split multiple instructions into smaller instruction that is replcacing works good in memory operations.

b)Memory access delay and subinstructions execution delay will be caused.

c)Here processor is single cycle so to find the cycles per instruction we have the formula

CPI =sum of (( Number of clock cycles of instruction * percentage of instruction)) / 100

here cycle is 1 and Load percentage is 30%.

total instructions in first statement is (3*30)/100 = 0.9

total instructions in second statement is (2*30)/100 = 0.6

Therefore second instruction is more efficient than first.