Post on 25-Feb-2016
description
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-1
ROB ExampleROB Example We will go through an example of the use of
reorder buffers in two scenarios— Completion without exceptions One instruction raises an exception
First, let’s consider the data structures in use for the example.
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-2
Entry Dest Result Exception Completed PC
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
TAILHEAD
FUs
RF
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value – 54 – 76 – -5 – -99
ReservationStations
R0
R1R2
R3
All valuesnow inreg. file Reservation stations
and ROB are empty
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-3
Code for the exampleCode for the example
A LW R2, 4(R0)
B MULT R3, R1, R2
C LW R2, 8(R0)
D ADD R1, R1, R2
E SUB R2, R0, R1
F ADD R0, R1, R2
At each step, we will show the changes by coloring the cell backgrounds pink.
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-4
Entry Dest Result Exception Completed PC
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
TAILHEAD
FUs
RF
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value – 54 – 76 – -5 – -99
ReservationStations
R0
R1R2
R3
A LW R2, 4(R0)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-5
Entry Dest Result Exception Completed PC
0 R2 A
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
TAILHEAD
FUs
RF
mytag
src1ready
src1tag/value
src2ready
src2tag/value
0 54 Imm=4
In RF tag value – 54 – 76
0 -5 – -99
ReservationStations
R0
R1R2
R3
A LW R2, 4(R0)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
Entries made inreservation station
and ROB
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-6
Entry Dest Result Exception Completed PC
0 R2 A
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
TAILHEAD
FUs
RF
mytag
src1ready
src1tag/value
src2ready
src2tag/value
0 54 Imm=4
In RF tag value – 54 – 76
0 –5 – – 99
ReservationStations
R0
R1R2
R3
B MULT R3, R1, R2
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-7
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
TAIL
HEAD
FUs
RF
mytag
src1ready
src1tag/value
src2ready
src2tag/value
1 76 0
In RF tag value – 54 – 76
0 – 5
1 –99
ReservationStations
R0
R1R2
R3
B MULT R3, R1, R2
0 (cache miss)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-8
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
TAIL
HEAD
FUs
RF
mytag
src1ready
src1tag/value
src2ready
src2tag/value
1 76 0
In RF tag value – 54 – 76
0 –5
1 –99
ReservationStations
R0
R1R2
R3
C LW R2, 8(R0)
0 (cache miss)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-9
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 C
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
2 54 Imm=8
1 76 0
In RF tag value – 54 – 76
2 –5
1 –99
ReservationStations
R0
R1R2
R3
C LW R2, 8(R0)
TAIL
0 (cache miss)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-10
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 C
3
4
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
2 54 Imm=8
1 76 0
In RF tag value – 54 – 76
2 –5
1 –99
ReservationStations
R0
R1R2
R3
D ADD R1, R1, R2
TAIL
0 (cache miss)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-11
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 C
3 R1 D
4
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
3 76 2
1 76 0
In RF tag value – 54
3 76
2 –5
1 –99
ReservationStations
R0
R1R2
R3
D ADD R1, R1, R2
TAIL
0 (cache miss)2 (cache hit)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-12
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 C
3 R1 D
4
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
3 76 2
1 76 0
In RF tag value – 54
3 76
2 –5
1 –99
ReservationStations
R0
R1R2
R3
E SUB R2, R0, R1
TAIL
0 (cache miss)2 (cache hit)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-13
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 C
3 R1 D
4 R2 E
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
4 54 3
3 76 2
1 76 0
In RF tag value – 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
E SUB R2, R0, R1
TAIL
0 (cache miss)2 (cache hit)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-14
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 no C
3 R1 D
4 R2 E
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
4 54 3
3 76 667
1 76 0
In RF tag value – 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)
2, 667, no exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-15
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 no C
3 R1 D
4 R2 E
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
4 54 3
1 76 0
In RF tag value – 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)3
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-16
667 + 76 = 743
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 no C
3 R1 743 no D
4 R2 E
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
4 54 743
1 76 0
In RF tag value – 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)
3, 743, no exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-17
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
1 76 0
In RF tag value – 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)
4, –689, no exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
54 – 743 = –689
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-18
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
1 76 0
In RF tag value – 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)
F ADD R0, R1, R2
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-19
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
5 743 –689
1 76 0
In RF tag value
5 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)
F ADD R0, R1, R2
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-20
Entry Dest Result Exception Completed PC
0 R2 A
1 R3 B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
1 76 0
In RF tag value
5 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0 (cache miss)
5, 54, no exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
743 + –689 = 54
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-21
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
1 76 650000
In RF tag value
5 54
3 76
4 –5
1 –99
ReservationStations
R0
R1R2
R3
TAIL
0, 650000, no exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-22
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54
3 76
4 650000
1 –99
ReservationStations
R0
R1R2
R3
TAIL
Reg=R2, Tag=0, Val=650000
Note: Tag doesn’t match RF tag, don’t set “In RF”Note: Commit value to register- file state
1 (multiply)
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0)
D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-23
Two scenarios next…Two scenarios next… Multiply
Scenario #1: Completes without exception Scenario #2: Raises exception
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-24
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 49400000 No B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54
3 76
4 650000
1 –99
ReservationStations
R0
R1R2
R3
TAIL
1, 49400000, no exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
650000 76 = 49400000
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-25
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 49400000 No B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54
3 76
4 650000 – 49400000
ReservationStations
R0
R1R2
R3
TAIL
Reg=R3, Tag=1, Val=49400000
Note: Tag matches RF tag, so set “In RF”Note: Commit value to register-file state
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0)
D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-26
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 49400000 No B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEADmytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54
3 76
4 667 – 49400000
ReservationStations
R0
R1R2
R3
TAIL
Reg=R2, Tag=2, Val=667
Note: Tag does not match RF tag, don’t set “In RF”Note: Commit value to register-file state
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0)
D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-27
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 49400000 No B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEADmytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54 – 743
4 667 – 49400000
ReservationStations
R0
R1R2
R3
TAIL
Reg=R1, Tag=3, Val=743
Note: Tag matches RF tag, so set “In RF”Note: Commit value to register-file state
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0)
D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-28
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 49400000 No B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54 – 743 – – 689 – 49400000
ReservationStations
R0
R1R2
R3
TAIL
Reg=R2, Tag=4, Val=–689
Note: Tag matches RF tag, so set “In RF”Note: Commit value to register-file state
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0)
D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-29
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 49400000 No B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value – 54 – 743 – –689 – 49400000
ReservationStations
R0
R1R2
R3
TAIL
Reg=R0, Tag=5, Val=54
Note: Tag matches RF tag, so set “In RF”Note: Commit value to register file state
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0)
D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-30
Now do scenario #2Now do scenario #2 Multiply raises exception.
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-31
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 – Yes B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value
5 54
3 76
4 650000
1 –99
ReservationStations
R0
R1R2
R3
TAIL
1, exception
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-32
Entry Dest Result Exception Completed PC
0 R2 650000 No A
1 R3 – Yes B
2 R2 667 No C
3 R1 743 No D
4 R2 –689 No E
5 R0 54 No F
6
7
8
9
10
11
12
13
14
15
ROB
FUs
RF
HEAD
mytag
src1ready
src1tag/value
src2ready
src2tag/value
In RF tag value – 54 – 76 – 650000 – –99
ReservationStations
R0
R1R2
R3
TAIL
A LW R2, 4(R0) B MULT R3, R1, R2C LW R2, 8(R0) D ADD R1, R1, R2 E SUB R2, R0, R1 F ADD R0, R1, R2
ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE,ECE 463/521, Profs. Conte, Rotenberg, & Gehringer, Dept. of ECE, NC State UniversityNC State University ILP-33
Other animationsOther animations Another good animation of reorder buffers is
the one by John Kubiatowicz. See www.cs.ccu.edu.tw/~chen/arch/reorder-step.ppt
orwww.cs.uit.no/studier/kurs/d241/info/2002h/notes/Berkeley/ Kubiatowicz-2001f/files/lectures/lec19-memory.ppt.
A higher-level visualization of the process is at http://www.ece.lsu.edu/koppel/see/