A prototype DAQ system for the ALICE experiment based on SCI

A prototype DAQ system for the ALICE/PHOS beam test and commissioning program is presented. The system has been taking data since august '97, and represents one of the first applications of the scalable coherent interface (SCI) as interconnect technology for an operational DAQ system. The front-end VMEbus address space is mapped directly from the DAQ computer memory space through SCI via PCI-SCI bridges. The DAQ computer is a commodity PC running the Linux operating system. The results of measurements of data transfer rate and latency for the PCI-SCI bridges in a PCVMEbus SCI-configuration are presented. An optical SCI link based on the Motorola Optobus I data link is described.