Alliant Computer Systems

Alliant Computer Systems was a computer company that designed and manufactured parallel computing systems. Together with Pyramid Technology and Sequent Computer Systems, Alliant's machines pioneered the symmetric multiprocessing market. One of the more successful companies in the group, over 650 Alliant systems were produced over their lifetime.

Alliant was founded, as Dataflow Systems, in May 1982 by Gruner, Mundie and McAndrew to produce machines for scientific and engineering users who needed smaller machines than offerings from Cray Computer and similar high-end vendors.

Alliant's first machines were announced in 1985, starting with the FX series. The FX series consisted of a number Computational Elements, or CEs, which included one, two or four Weitek 1064 FPU's and several custom designed support chips to implement a vector processor based on it. These were controlled by the Interactive Processors, IPs, which were based on Motorola 68008's with 4MB of local RAM, connecting everything together using a crossbar system. Like many early multiprocessing systems, the FX series ran an adapted version of BSD Unix on the IPs, known as Concentrix. Systems were named for the number of CEs inside, the FX/1, FX/4 and FX/8. Alliant machines were fairly small, the FX/1 was about the size of a large full-height PC, while the FX/8 was smaller than a VAX 11/750, about the size of a large photocopier. Speed was excellent, the FX/1 about 2.5 MIPS (as opposed to the 1 MIPS VAX 11/780), while the FX/8 was some 5 times faster.

A second series of FX machines included more custom hardware known as Advanced Computational Elements (ACE). The Weitek FPUs were replaced by their own design known as the BIT, which included a custom vector processor with 32 64-bit elements, and 8 64-bit scalar floating point, 8 32-bit integer, and 8 32-bit address registers. These were used in the FX/40, FX/80 and VFX machines.

The FX/2800 series replaced the CE/ACEs and IPs with modules based on the Intel i860 RISC chip. The i860 was an early superscalar CPU that allowed the programmer access directly into the pipelines; with custom coding the 860 was a very fast system, making it perfect for supercomputer applications. In the new series the Super Computational Element (SCE) and Super Interactive Processor (SIP) both consisted of up to four i860s, up to seven of which could be interconnected on the crossbar. A fully-expanded FX/2800 could support 28 i860's in total.

In 1990 Alliant purchased Raster Technologies, a provider of high-resolution graphics terminals and custom graphics cards for Sun Microsystems workstations. Their GX4000 product was a combination of PHIGS+ software and special graphical boards that could generate and display graphical vectors very fast. For 3D effects, a hardware Z-buffer was available.

Aliiant's final product series was the CAMPUS/800, a massively-parallel machine based on units similar to the FX/2800 known as ClusterNodes and sharing a total of up to 4GB of unified memory. Each ClusterNode was connected to up to 32 others with a intra-ClusterNode switch, with a latency of 1us and 1.12GB/s bandwidth. An inter-ClusterNode switch based on HIPPI was also available, with a latency of 30us and 2.56GB/s bandwidth. The largest CAMPUS system created included 192 ClusterNodes in total, and provided 4.7 GFLOPS.

The CAMPUS/800 was first announced in 1991, but the company was hit by a series financial problems and went bankrupt in 1992. Various Alliant systems soldiered on in service for many years after that however, and were generally considered very reliable.