CS 3853 Computer Architecture Chapter 3 Section 4 Example Answers

Modifaction 2: Two multiply functional units

Instruction		Reservation Station	Execution Unit	Issue Cycle	Ex Start Cycle	Ex End Cycle	Memory Cycle	CDB cycle	Write dest
L.D	F6,32(R2)	Load1	ALU	1	2	2	3	4	F6
L.D	F2,44(R3)	Load2	ALU	2	3	3	4	5	F2
MUL.D	F0,F2,F4	Mult1	fmul	3	6	15		16	F0
SUB.D	F8,F2,F6	Add1	fadd	4	6	7		8	F8
DIV.D	F10,F0,F6	Mult2	fmul	5	17	56		57	F10
ADD.D	F6,F8,F2	Add2	fadd	6	9	10		11	F6

Note 1: No change since Mult2 cannot execute until F0 is ready.
Note 2: If the functional unit is available at the same time it puts its reuslt on the CDB, the DIV.D could start one cycle earlier.