This document compares specifications of three Cray supercomputers from 1976, 1985, and 1990. The Cray 1 from 1976 had a clock speed of 80 MHz, 4 MB of RAM, and could perform over 80 million floating point operations per second. The Cray XMP from 1985 had four CPUs with a clock speed of 118 MHz each, 32 MB of total RAM, 2 GB of disk storage, and could perform 220 Mflops. The Cray YMP from 1990 had eight CPUs with a clock speed of 166 MHz each, 512 MB of total RAM, 2 GB of disk storage, and could perform 1000 Mflops.