The COTS Approach to the Read-Out Crate in ATLAS DAQ Prototype -1

A prototyping project has been undertaken by the ATLAS DAQ and Event Filter group. The aim is to design and implement a fully functional vertical slice of the ATLAS DAQ and Event Filter with maximum use of Commercial Off The Shelf components (COTS). The Read-Out Crate is a modular component within the vertical slice whose principle functionality is to receive, buffer and forward detector data to the Event Filter systems via an event building network and to the Level 2 Trigger. As required by the project, the initial implementation is based on commercial components, namely VMEbus, PowerPC based single board computers and the Lynx-OS real-time operating system. The measured performance is compared to the results of a discrete event simulation of the Read-Out Crate using the PTOLEMY modelling tool. It has allowed us to model and study the Read-Out Crate performance based on a mixture of existing and forthcoming technologies, an example of the latter being VMEbus 2eSST, and different architectures. Results from studies in this area are also presented. The design and initial implementation of the Read-Out Crate is presented.