CHAPTER 2 V
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Preliminary User’s Manual S15543EJ1V0UM
2.3.4.5 Load word instruction (LW rt, offset (base))
IF stage
Same as the IF stage for the ADD instruction.
IT stage
Same as the IT stage for the ADD instruction.
RF stage
Same as the RF stage for the ADD instruction. Note that the base field is in the same position
as the rs field.
EX stage
Refer to the EX stage for the ADD instruction. For LW, the inputs to the ALU come from
GPR[base] through the bypass multiplexer and from the sign-extended offset field. The result
of the ALU operation that is latched into the ALU output latch in
Φ
1 represents the effective
virtual address of the operand (DVA).
DC stage
The cache tag field is compared with the Page Frame Number (PFN) field of the TLB entry.
After passing through the load aligner, aligned data is placed in the DC output latch during
Φ
2.
WB stage
During
Φ
1, the cache read data is written into the register file addressed by the rt field.
Figure 2-17. LW Instruction Pipeline Activities (In MIPS III Instruction Mode)
IF1
Cycle
Phase
PCycle
PClock
IF2
Φ
2
Φ
1
Φ
2
Φ
1
Φ
2
Φ
1
Φ
2
Φ
1
Φ
2
Φ
1
RF1
RF2
EX1
EX2
DC1
DC2
WB1
WB2
ITLB
IDC
ITC
ICA
IDEC
WB
DVA
EX
RF
DCA
DL
DTLB
DT