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Chapter 6. Instruction Timing
6-39
Instruction Latency Summary
6.6.1.3 Completion Unit Resource Requirements
The following is a list of resources required to avoid stalls in the completion unit; note that
the two completion entries are described as CQ[0] and CQ[1], where CQ[0] is the CQ
located at the end of the CQ (see Figure 6-4).
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Requirements for completing an instruction from CQ[0] are as follows:
Instruction in CQ[0] must be Tnished.
Instruction in CQ[0] must not follow an unresolved predicted branch.
Instruction in CQ[0] must not cause an exception.
Requirements for completing an instruction from CQ[1] are as follows:
Instruction in CQ[0] must complete in same cycle.
Instruction in CQ[1] must be Tnished.
Instruction in CQ[1] must not follow an unresolved predicted branch.
Instruction in CQ[1] must not cause an exception.
Instruction in CQ[1] must be an integer, load,
dcbt
, data streaming, or AltiVec
instruction.
Number of CR updates from both CQ[0] and CQ[1] must not exceed two.
Number of GPR updates from both CQ[0] and CQ[1] must not exceed two.
Number of FPR updates from both CQ[0] and CQ[1] must not exceed two.
Number of VR updates from both CQ[0] and CQ[1] must not exceed two.
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6.7 Instruction Latency Summary
Instruction timing in number of processor clock cycles is shown in Table 6-3 through
Table 6-9. The latency tables use the following conventions:
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Pipelined load /store instructions are shown with cycles of total latency and
throughput cycles separated by a colon.
The variable b represents the processor/system-bus clock ratio.
Broadcast indicates a bus broadcast that has a minimum value of 3*b.
Pipelined oating-point instructions are shown with number of clocks in each
pipeline stage separated by dashes.
In addition, additional cycles due to serializations are indicated in the cycles column
with the following:
c (completion serialization)
s (store serialization)
y (sync serialization)
e (execution serialization)
r (refetch serialization)
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