Functional Unit Hazards
6-22
Table 6–4 shows the instruction hazards for DP compare instructions execut-
ing on the .S unit.
Table 6–4. DP Compare .S-Unit Instruction Hazards
Instruction Execution
Cycle
1
2
3
DP compare
R
RW
Instruction Type
Subsequent Same-Unit Instruction Executable
Single-cycle
Xrw
n
DP compare
Xr
n
2-cycle DP
Xrw
n
Branch
†
Xr
n
Instruction Type
Same Side, Different Unit, Both Using Cross Path Executable
Single-cycle
Xr
n
Load
Xr
n
Store
Xr
n
INTDP
Xr
n
ADDDP/SUBDP
Xr
n
16
16 multiply
Xr
n
4-cycle
Xr
n
MPYI
Xr
n
MPYID
Xr
n
MPYDP
Xr
n
Legend:
E1 phase of the single-cyle instruction
R
Sources read for the instruction
W
Destinations written for the instruction
n
Next instruction can enter E1 during cycle
Xr
Next instruction cannot enter E1 during cycle–read/decode hazard
Xrw
Next instruction cannot enter E1 during cycle–read/decode/write hazard
†
The branch on register instruction is the only branch instruction that reads a
general-purpose register