An apparatus and methods for hardware-based performance monitoring of a computer system are presented. The apparatus includes: processing units; a memory; a connector device connecting the processing units and the memory; probes inserted the processing units, and the probes generating probe signals when selected processing events are detected; and a thread trace device connected to the connector device. The thread trace device includes an event interface to receive probe signals, and an event memory controller to send probe event messages to the memory, where probe event messages are based on probe signals. The probe event messages transferred to memory can be subsequently analyzed using a software program to determine, for example, thread-to-thread interactions.