  We developed a PCI interface for GRAPE systems. GRAPE(GRAvity piPE) is a
special-purpose computer for gravitational N-body simulations. A GRAPE system
consists of GRAPE processor boards and a host computer. GRAPE processors
perform the calculation of gravitational forces between particles. The host
computer performs the rest of calculations. The newest of GRAPE machines, the
GRAPE-4, achieved the peak performance of 1.08 Tflops. The GRAPE-4 system uses
TURBOChannel for the interface to the host, which limits the selection of the
host computer. The TURBOChannel bus is not supported by any of recent
workstations. We developed a new host interface board which adopts the PCI bus
instead of the TURBOChannel. PCI is an I/O bus standard developed by Intel. It
has fairly high peak transfer speed, and is available on wide range of
computers, from PCs to supercomputers. Thus, the new interface allows us to
connect GRAPE-4 to a wide variety of host computers. In test runs with a
Barnes-Hut treecode, we found that the performance of new system with PCI
interface is 40% better than that of the original system.
