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Pipeline Execution of Instruction Types
Pipeline4-24 SPRU733
4.2.6 Two-Cycle DP Instructions
Two-cycle DP instructions use both the E1 and E2 phases of the pipeline to
complete their operations (see Table 4−8). The following instructions are
two-cycle DP instructions:
ABSDP
RCPDP
RSQDP
SPDP
The lower and upper 32 bits of the DP source are read on E1 using the src1
and src2 ports, respectively. The lower 32 bits of the DP source are written on
E1 and the upper 32 bits of the DP source are written on E2. The two-cycle DP
instructions are executed on the .S units. The status is written to the FAUCR
on E1. Figure 4−18 shows the fetch, decode, and execute phases of the pipe-
line that the two-cycle DP instructions use.
Table 4−8. Two-Cycle DP Instruction Execution
Pipeline Stage
E1 E2
Read src2_l
src2_h
Written dst_l dst_h
Unit in use
.S
Figure 4−18. Two-Cycle DP Instruction Phases
PG PS PW PR DP DC E1 E2
1 delay slot