This paper presents HAL's Mercury Interconnect Architecture, an interconnect infrastructure designed to link commodity microprocessors, memory, and I/O components into high-performance multiprocessing servers. Both shared-memory and message-passing systems, as well as hybrid systems are supported by the interconnect. The key attributes of the Mercury Interconnect Architecture are: low latency, high bandwidth, a modular and flexible design, reliability/availability/serviceability (RAS) features, and a simplicity that enables very cost-effective implementations. The first implementation of the architecture links multiple 4-processor Pentium™ Pro based nodes. In a 4-node (16-processor) shared-memory configuration, this system achieves a remote read latency of just over 1 µs, and a maximum interconnect bandwidth of 6.4 GByte/s. Both of these parameters far outpace comparable SCI-based solutions, while utilizing much fewer hardware components.