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Pipeline Execution of Instruction Types
4-25PipelineSPRU733
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