  The first stage of the ATLAS Fast TracKer (FTK) is an ATCA-based input
interface system, where hits from the entire silicon tracker are clustered and
organized into overlapping eta-phi trigger towers before being sent to the
tracking engines. First, FTK Input Mezzanine cards receive hit data and perform
clustering to reduce data volume. Then, the ATCA-based Data Formatter system
will organize the trigger tower data, sharing data among boards over full mesh
backplanes and optic fibers. The board and system level design concepts and
implementation details, as well as the operation experiences from the FTK
full-chain testing, will be presented.
