GRAPE: a special-purpose computer for N-body problems

GRAPE (GRAvity PipE) is a special-purpose computer designed to accelerate the numerical integration of the astrophysical N-body problem. The prototype hardware, GRAPE-1, is designed as the backend processor that calculates the gravitational interaction between particles. All other calculations are performed on the host computer connected to GRAPE-1. For large-N calculations (N ≳10⁴), GRAPE-1 achieves about 200 Mflops equivalent in one board of the size of about 40 cm by 30 cm, consuming 2.5 W of power. The specialized pipelined architecture of the GRAPE-1 optimized for the large N calculation is the key to the high performance. The authors describe the design, construction and programming of GRAPE-1. The architecture is quite simple, and it is easy to put one pipeline into one LSI chip and make many pipelines work in parallel, without creating a communication bottleneck