The E769 Multiprocessor Based Data Acquisition System

The Data Acquistion system at Fermilab´s Tagged Photon Lab has been significantly upgraded by replacing a conventional minicomputer (PDP/11) based system reading out Camac front end modules via the Camac branch highway with a VME based multiprocessor system fed by smart crate controllers via high-speed parallel data paths. The input data rate has been increased from 350 Kb/s to 1.5 Mb/s (100 events /sec to 450 events /sec) while the dead time has decreased from 3 ms to .7 ms per event. Furthermore, a great deal of online computing power (70 ms of Vax11/780 equivalent time per event) is available for online processing. An overview of both the hardware and the software is given, along with more in depth discussions of four software issues.