Pipeline Operation Overview
6-6
6.1.4
Summary of Pipeline Operation
Figure 6–5 shows all the phases in each stage of the ’C67x pipeline in sequen-
tial order, from left to right.
Figure 6–5. Floating-Point Pipeline Phases
Fetch
Execute
Decode
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
Figure 6–6 shows an example of the pipeline flow of consecutive fetch packets
that contain eight parallel instructions. In this case, where the pipeline is full,
all instructions in a fetch packet are in parallel and split into one execute packet
per fetch packet. The fetch packets flow in lockstep fashion through each
phase of the pipeline.
For example, examine cycle 7 in Figure 6–6. When the instructions from FP n
reach E1, the instructions in the execute packet from FPn +1 are being
decoded. FP n + 2 is in dispatch while FPs n + 3, n + 4, n + 5, and n + 6 are
each in one of four phases of program fetch. See section 6.4,
Performance
Considerations, on page 6-52 for additional detail on code flowing through the
pipeline.
Figure 6–6. Pipeline Operation: One Execute Packet per Fetch Packet
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Clock cycle
ÁÁÁÁ
ÁÁÁÁ
Fetch
packet
ÁÁ
ÁÁ
1
ÁÁÁ
ÁÁÁ
2
ÁÁ
ÁÁ
3
ÁÁÁ
ÁÁÁ
4
ÁÁÁ
ÁÁÁ
5
ÁÁ
ÁÁ
6
ÁÁÁ
ÁÁÁ
7
ÁÁ
ÁÁ
8
ÁÁÁ
ÁÁÁ
9
ÁÁ
ÁÁ
10
ÁÁÁ
ÁÁÁ
11
ÁÁ
ÁÁ
12
ÁÁÁ
ÁÁÁ
13
ÁÁ
ÁÁ
14
ÁÁÁ
ÁÁÁ
15
ÁÁÁ
ÁÁÁ
16
ÁÁ
ÁÁ
17
ÁÁÁÁ
ÁÁÁÁ
n
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
ÁÁÁÁ
ÁÁÁÁ
n+1
ÁÁ
ÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
ÁÁÁÁ
ÁÁÁÁ
n+2
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
E7
E8
E9
ÁÁÁÁ
ÁÁÁÁ
n+3
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
E7
E8
ÁÁÁÁ
n+4
ÁÁ
ÁÁÁ
ÁÁ
ÁÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
E7
ÁÁÁÁ
ÁÁÁÁ
n+5
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
E6
ÁÁÁÁ
ÁÁÁÁ
n+6
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
E5
ÁÁÁÁ
ÁÁÁÁ
n+7
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
ÁÁÁÁ
ÁÁÁÁ
n+8
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
E3
ÁÁÁÁ
ÁÁÁÁ
n+9
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
PG
PS
PW
PR
DP
DC
E1
E2
ÁÁÁÁ
n+10
ÁÁ
ÁÁÁ
ÁÁ
ÁÁÁ
ÁÁÁ
ÁÁ
ÁÁÁ
ÁÁ
ÁÁÁ
ÁÁ
PG
PS
PW
PR
DP
DC
E1