CompactPCI based data acquisition with MDSplus

Alcator C-Mod is incorporating CompactPCI based data acquisition cards into the MDSplus data acquisition system. Each crate includes a diskless computer running the mdsip server from MDSplus under the Linux operating system, and one or more digitizer cards with onboard memory. A minimal set of software is downloaded to this computer at boot time allowing it to arm and read out the cards when requested by the host data acquisition computers. This diskless design is very attractive in our high field environment and simplifies the maintenance and configuration of the embedded computers. Separating the digitizers from the data acquisition computers allows the data acquisition to be done in a platform independent way. Ethernet provides robust, inexpensive communications. The initial digitizer cards have thirty-two 16 bit, 250 KHz digitizers, 128 Msamples of memory, two arbitrary waveform generators and eight programmable digital outputs. CompactPCI provides an attractive alternative to our aging CAMAC based data acquisition equipment.