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Intel
®
IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
September 2006 DM
Order Number: 252480-006US 169
Intel XScale
®
Processor—Intel
®
IXP42X product line and IXC1100 control plane processors
3.10.2.1.2 Intel
®
IXP42X Product Line of Network Processors and IXC1100 Control Plane
Processor Pipeline Organization
The IXP42X product line and IXC1100 control plane processors single-issue super-
pipeline consist of a main execution pipeline, MAC pipeline, and a memory access
pipeline. These are shown in Figure 29, with the main execution pipeline shaded.
Table 93 gives a brief description of each pipe-stage.
3.10.2.1.3 Out-of-Order Completion
Sequential consistency of instruction execution relates to two aspects: first, to the
order in which the instructions are completed; and second, to the order in which
memory is accessed due to load and store instructions. The IXP42X product line and
IXC1100 control plane processors preserve a weak processor consistency because
instructions may complete out of order, provided that no data dependencies exist.
Figure 29. Processors’ RISC Super-Pipeline
F1 F2 ID RF X1 X2
XWB
M1 M2 Mx
D1 D2
DWB
Main execution pipeline
MAC pipeline
Memory pipeline
Table 93. Pipelines and Pipe Stages
Pipe / Pipe State Description Covered In
Main Execution Pipeline Handles data processing instructions
“Main Execution Pipeline” on
page 171
IF1/IF2 Instruction Fetch “
ID Instruction Decode “
RF Register File / Operand Shifter “
X1 ALU Execute “
X2 State Execute “
XWB Write-back “
Memory Pipeline Handles load/store instructions “Memory Pipeline” on page 172
D1/D2 Data Cache Access “
DWB Data cache writeback “
MAC Pipeline Handles all multiply instructions
“Multiply/Multiply Accumulate
(MAC) Pipeline” on page 173
M1-M5 Multiplier stages “
MWB (not shown) MAC write-back - may occur during M2-M5 “