A hardware and software overview of the Delphi contiguity trigger

The contiguity processor of the Delphi detector, which is composed of 12 Fastbus modules (one for each time-projection-chamber sector), is the main second-level track trigger component in the experiment. More than 3000 MIPS (million instructions per second) of processing power are achieved by 4608 processing elements (PEs) packed in specially designed application-specific integrated circuits. High interconnectivity among PEs (bidimensional lattice) and a highly parallel algorithm (contiguity mask) allow a three-dimensional vertex reconstruction less than 5 μs. An overview of the single-instruction multiple-data architecture together with the programming language and the interactive debugging tools for the processor are given