The Event Builder and Level3 systems constitute critical
components of the DAQ in the CDF experiment at Fermilab.  These systems are
responsible for collecting data fragments from the front end electronics,
assembling the data into complete event records, reconstructing the events,
and forming the final trigger decision.

With Tevatron Run IIa in progress, the systems have been running
successfully at high throughput rates, the design utilizing scalable
architecture and distributed event processing to meet the requirements.  A
brief description current performance in Run IIa and possible upgrade for
Run IIb is presented.