The on-line computational and control system for the 4 pi-detector CHIMERA.

A commercial two-DSP-based board is the basic unit of the on-line computati onal and control system under development for the multidetector array CHIME RA. The system design includes a small scale parallel and distributed archi tecture of PCs and DSP boards. The PCs are used both as host computer and i nterface between user and network. Each PC can host up to three DSP boards. The system is able to accomplish the on-beam control of CHIMERA, by means of the on-line computation of special algorithms, instead of using the usua l techniques of special pulses to be sent off-beam. The physical data, coll ected and organized in UDP packets by the data acquisition system, are read through a 10 Mbit/s Ethernet network. The PC software, running under Windo ws NT 4.0, is based on threads and assures the communication and program ma naging as well as the result presentation. The DSP-software is written in C ++ and takes care of the communication with the PC and of the computation o f algorithms. The preliminary on beam results for the first three-wheels (a bout 100 telescopes), obtained by employing two biprocessor boards located in the PCI bus of a Pentium MMX PC, are also presented.