Highly Parallelized Pattern Matching Execution for the ATLAS Experiment

The trigger system of the ATLAS experiment at LHC will extend its rejection capabilities during operations in 2015-2018 by introducing the Fast TracKer system (FTK). FTK is a hardware based system capable of finding charged particle tracks by analyzing hits in silicon detectors at the rate of 105 events per second. The core of track reconstruction is performed into two pipelined steps. At first step the candidate tracks are found by matching combination of low resolution hits to predefined patterns; then they are used in the second step to seed a more precise track fitting algorithm. The key FTK component is an Associative Memory (AM) system that is used to perform pattern matching with high degree of parallelism. The AM system implementation, the AM Serial Link Processor, is based on an extremely powerful network of 2 Gb/s serial links to sustain a huge traffic of data. We report on the design of the Serial Link Processor consisting of two types of boards, the Little Associative Memory Board (LAMB), a mezzanine where the AM chips are mounted, and the Associative Memory Board (AMB), a 9U VME motherboard which hosts four LAMB daughterboards. We also report on the performance of the prototypes (both hardware and firmware) produced and tested in the global FTK integration, an important milestone to be satisfied before the construction of the final FTK system.