Chapter 3
48 MIPS R4000 Microprocessor User's Manual
3.3 Branch Delay
The CPU pipeline has a branch delay of three cycles and a load delay of
two cycles. The three-cycle branch delay is a result of the branch
comparison logic operating during the EX pipeline stage of the branch,
producing an instruction address that is available in the IF stage, four
instructions later.
Figure 3-3 illustrates the branch delay.
Figure 3-3 CPU Pipeline Branch Delay
3.4 Load Delay
The completion of a load at the end of the DS pipeline stage produces an
operand that is available for the EX pipeline stage of the third subsequent
instruction.
Figure 3-4 shows the load delay of two pipeline stages.
Figure 3-4 CPU Pipeline Load Delay
branch
target
Branch Delay
three branch
delay
instructions
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
IF IS RF EX DF DS TC WB
load
f(load)
Load
two load
delay
instructions
Delay
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