A PowerPC based readout system for the silicon trackers of the H1-experiment

The readout system of the H1 Central and Backward Silicon Tracker detectors is processing the data of about 120 000 analog readout channels. The strip data are digitized and processed by VMEbus Readout Processor Modules equipped with a local PCI bus and a 96 MHz PowerPC 604 processor. The processor performs a cluster search and reduces the raw data size by an average factor of 40. It also updates the pedestals and noise variances periodically. Events can be processed at up to 100 Hz, well matching the second level trigger rates.