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The Unabridged Pentium 4 IA32 Processor Genealogy by Bob Colwell, Tom Shanley

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The μop Pipeline's Major Elements

The Allocator

General

The Allocator was introduced in “The Allocator Stage” on page 931. Refer to Figure 38-37 on page 939. In the Allocator stage, for each of the three in-order μops the following core resources are allocated (i.e., reserved to be used by the three μops as they pass through the pipeline):

  • One of the 126 Reorder Buffer (ROB) entries is reserved to track the μop's completion status.

  • One of the 128 integer Register File (RF) entries or FP RF entries is reserved to hold the result data that will be produced by the μop when it is executed.

  • If the instruction is a load or a store, one of the 48 load or 24 store buffer entries is reserved to handle the load or store when it is executed.

  • An entry is reserved ...

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