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==== Execution engine ====
 
==== Execution engine ====
Continuing with the decoder is the [[register renaming]] stage. This is crucial for out-of-order execution. In this stage the architectural x86 registers get mapped into one of the many physical registers. The integer physical register file (PRF) has been enlarged by 8 addition registers for a total 168. Likewise the FP PRF was extended by 24 registers bringing it too to 168 registers. The larger increase in the FP PRF is likely to accommodate the new {{x86|AVX2}} extension. The [[reorder buffer|ROB]] in Haswell has been increased to 192 entries (from 168 in Ivy) where each entry corresponds to a single µOp. The ROB is fixed split between the two threads. Additional scheduler resources get allocated as well - this includes stores, loads, and branch buffer entries. Note that due to how dependencies are handled, there may be more or less µOps than what was fed in. For the most part, the renamer is unified and deals with both integers and vectors. Resources, however, are partitioned between the two threads. Finally, as a last step, the µOps are matched with a port depending on their intended execution purpose. Up to 4 fused µOps may be renamed and handled per thread per cycle. Both the load and store in-flight units were increased to 72 and 42 entries respectively.
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Continuing with the decoder is the [[register renaming]] stage. This is crucial for out-of-order execution. In this stage the architectural x86 registers get mapped into one of the many physical registers. The integer physical register file (PRF) has been enlarged by 8 addition registers for a total 168. Likewise the FP PRF was extended by 24 registers bringing it too to 168 registers. The larger increase in the FP PRF is likely to accommodate the new {{x86|AVX2}} extension. The [[reorder buffer|ROB]] in Haswell has been increased to 192 entries (from 168 in Ivy) where each entry corresponds to a single µOp. The ROD is fixed split between the two threads. Additional scheduler resources get allocated as well - this includes stores, loads, and branch buffer entries. Note that due to how dependencies are handled, there may be more or less µOps than what was fed in. For the most part, the renamer is unified and deals with both integers and vectors. Resources, however, are partitioned between the two threads. Finally, as a last step, the µOps are matched with a port depending on their intended execution purpose. Up to 4 fused µOps may be renamed and handled per thread per cycle. Both the load and store in-flight units were increased to 72 and 42 entries respectively.
  
 
Haswell continues to use a unified scheduler for all µOps which holds 60 entries. µOps at this stage sit idle until they are cleared to be  executed via their assigned dispatch port. µOps may be held due to resource unavailability.
 
Haswell continues to use a unified scheduler for all µOps which holds 60 entries. µOps at this stage sit idle until they are cleared to be  executed via their assigned dispatch port. µOps may be held due to resource unavailability.

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codenameHaswell +
core count2 +, 4 +, 6 +, 8 +, 16 +, 10 +, 12 +, 14 + and 18 +
designerIntel +
first launchedJune 4, 2013 +
full page nameintel/microarchitectures/haswell (client) +
instance ofmicroarchitecture +
instruction set architecturex86-64 +
manufacturerIntel +
microarchitecture typeCPU +
nameHaswell +
phase-out2015 +
pipeline stages (max)19 +
pipeline stages (min)14 +
process22 nm (0.022 μm, 2.2e-5 mm) +