The Testbed for Distributed Processing, or Ted, consists of Intel Corp.'s iSBC 8086 single board computers (SBCs) organized into groups or clusters. Each cluster consists of several SBCs that communicate via a shared memory. Intercluster communication occurs through an Ethernet interface. A hardware monitor designed and implemented to handle the monitoring activities within a cluster in the Ted system is described. By using specified patterns and don't-care masks, the system can detect accesses to selected data, addresses, or blocks of addresses. This function helps monitor events such as the access or usage of a memory location or a group of mailbox addresses. It also determines the amount of time consumed by the performance of specific operations. >