BBN Butterfly

The BBN Butterfly was a massively parallel computer from the 1980s. It was named for the "butterfly" multi-stage switching network around which it was built. Each machine had up to 512 CPUs, each with local memory, which could be connected to allow every CPU access to every other CPU's memory, although with a substantially greater latency (roughly 15:1) than for its own. The CPUs were commodity microprocessors.

The first generation used Motorola 68000 processors, followed by a 68010 version. The Butterfly connect was developed specifically for this computer. The second or third generation, GP-1000 models used Motorola 68020's and scaled to 256 CPUs. The later, TC-2000 models used Motorola 88100's, and scaled to 512 CPUs.

The Butterfly was initially developed as the VoiceFunnel, a router for the ST-II protocol intended for carrying voice and video over wideband networks. The Butterfly hardware was later used for the router of DARPA's high-speed descendant of ARPANET, the Satellite Wideband Network. This network later became the Terrestrial Wideband Network.

The Butterfly began with a proprietary operating system called Chrysalis, but moved to a Mach kernel operating system in 1989. While the memory access time was non-uniform, the machine had SMP memory semantics, and could be operated as a symmetric multiprocessor.

TotalView, the parallel program debugger developed for the Butterfly outlived the platform, to be ported to a number of other massively parallel machines.

* See also: Pluribus was earlier multiprocessor designed at BBN.