Review Assignment 3

- First tthing we had to do was reverse engineer what the loop execution path is.

R1 = 0 R1 = 2 R1 = 4
N
1

0
T

-2
2
NT

	B1		B2		B3
R1 = 0	act		act		act
	N		T		N
R1 = 2	N		T		T
R1 = 4	T		N		N


	R1 = 0		R1 =2		R1 = 4
	1		3
	N		N		T

	0		2		3
	T		T		N
					4
	-2		0		2
	2		0		2
	N		T		N


	B1		B2		B3
R1=?	PRED	ACT	PRED	ACT	PRED	ACT
0	N/N	N	N/N	T	N/N	N
2	N/N	N	T/N	T	N/N	T
4	N/N	T	T/N	N	N/T	N
0	N/T	N	T/N	T	N/T	N
2	N/T	N	T/N	T	N/N	T
4	N/T	T	T/N	N	N/T	N

			total of 5/18 missed predictions
			0.28
			2/9 miss predictons thereafter for this sequence.
			0.22
			Because the ones for the first two columns are correctly seeded and will not miss going forward. But the third column will still flip flop.


	Now we neeed to make one predictor that has 4 states.
	Begin by considering B3
	(0,2) predictor.

				required	N	T	N	N	T	N
	Consider B3 sequence:			actual	N	T	N	N	T	N

	design this predictor to give you that sequence.

	Consider B1 sequence			required	N	N	T	N	N	T
				actual	N	T	T	N	N	T

	Consider B2 sequence			required	t	t	n	t	t	n
				actual	n	t	n	t	n	n


	What if we now see the traditional loopy code sequence
	T	T	T	T	T	T	N	REQ
	N	T	N	T	N	T	T	ACT