The Balance multiprocessor system

A description is given of the architecture, operating system, and performance of Balance, a shared-memory, tightly coupled multiprocessor system. Balance can contain two to thirty 32-bit microprocessors with an aggregate performance of up to 21 million instructions per second (MIPS). Each processor has a private cache as well as a small local memory to hold frequently used kernel routines. The system features a high-bandwidth pipelined bus, up to 28 Mbytes of main memory, a diagnostic and console processor, up to four IEEE 769 (Multibus) adapters, an IEEE 802.3 (Ethernet) LAN interface, and an ANSI Small Computer System Interface (SCSI). Dynix, a multiprocessor operating system supporting both the 4.2 BSD and System V Unix environments, manages Balance, providing transparent support for multiprocessing as well as tools and libraries for developing parallel applications. The various subsystems and the Dynix operating system are examined. Applications and performance are discussed.<>