The ATLAS FTK Auxiliary Card: A Highly Functional VME Rear Transition Module for a Hardware Track Finding Processing Unit

The ATLAS Fast TracKer is a hardware-based track finder for the ATLAS High Level Trigger. Pattern recognition and preliminary track fitting are performed by VME Processing Units consisting of an Associative Memory Board (AMB) containing custom associative memory chips for pattern recognition, and the Auxiliary Card (AUX), a powerful rear transition module which formats the data for the AMB and performs linearized fits on AMB track candidates. We report on the design and testing of the AUX, which utilizes six FPGAs to process up to 32 Gbps of hit data and fit one track candidate per nanosecond.