GF11 is a parallel computer operational at IBM's T.J. Watson Research Center. It is based on the SIMD (Single Instruction Multiple Data) model of parallel computing. GF11 attains its peak execution rate of 11.3 Gigaflops by using 566 identical processing elements, each capable of delivering 20 Megaflops. The processors communicate through a 576× 576 Benes network. The network provides 11.3 Gigabytes/sec of communication bandwidth to the processors and allows the processors to dynamically reconfigure themselves into arrays of various dimensions and sizes or other patterns such as a tree, hypercube, etc. GF11 has several architectural enhancements to circumvent the limitations of the standard SIMD model. Preliminary benchmarking efforts on some applications indicate that near peak performance can be sustained on most applications. The architecture of GF11 is summarized in this paper and implementation of matrix multiplication, shallow water equations, and galaxy formation codes are discussed. © 1992.