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N/B Maintenance
N/B Maintenance
Level 1 Execution Trace Cache:
In addition to the 8KB data cache, the Pentium 4 processor includes an Execution Trace Cache that stores
up to 12K decoded micro-ops in the order of program execution. This increases performance by removing
the decoder from the main execution loop and makes more efficient usage of the cache storage space since
instructions that are branched around are not stored. The result is a means to deliver a high volume of
instructions to the processor’s execution units and a reduction in the overall time required to recover from
branches that have been mis-predicted.
Rapid Execution Engine:
Two Arithmetic Logic Units (ALUs) on the Pentium 4 processor are clocked at twice the core processor
frequency. This allows basic integer instructions such as Add, Subtract, Logical AND, Logical OR, etc. to
execute in half a clock cycle. For example, the Rapid Execution Engine on a 1.50 GHz Pentium 4 processor
runs at 3 GHz.
256KB, Level 2 Advanced Transfer Cache:
The Level 2 Advanced Transfer Cache (ATC) is 256KB in size and delivers a much higher data throughput
channel between the Level 2 cache and the processor core. The Advanced Transfer Cache consists of a 256-
bit (32-byte) interface that transfers data on each core clock. As a result, the Pentium 4 processor 1.50 GHz
can deliver a data transfer rate of 48 GB/s. This compares to a transfer rate of 16 GB/s on the Pentium III
processor at 1 GHz. Features of the ATC include:
Non-Blocking, full speed, on-die Level 2 cache
8-way set associativity
256-bit data bus to the level 2 cache
Data clocked into and out of the cache every clock cycle
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