Pipeline Execution of Instruction Types
4-25
Pipeline
SPRU733
4.2.7 Four-Cycle Instructions
Four-cycle instructions use the E1 through E4 phases of the pipeline to
complete their operations (see Table 4
−
9). The following instructions are
four-cycle instructions:
ADDSP
DPINT
DPSP
DPTRUNC
INTSP
MPYSP
SPINT
SPTRUNC
SUBSP
The sources are read on E1 and the results are written on E4. The four-cycle
instructions are executed on the .M or .L units. The status is written to the
FMCR or FADCR on E4. Figure 4
−
19 shows the fetch, decode, and execute
phases of the pipeline that the four-cycle instructions use.
Table 4
−
9. Four-Cycle Instruction Execution
Pipeline Stage
E1
E2
E3
E4
Read
src1
src2
Written
dst
Unit in use
.L or .M
Figure 4
−
19. Four-Cycle Instruction Phases
PG
PS
PW
PR
DP
DC
E1
E2
E3
E4
3 delay slots