Milpitas-based Appro International, a developer of clustered, high performance computing (HPC) systems, has been acquired by supercomputer maker Cray. Cray said it will pay $25M in cash for Appro, and make the firm its new Cluster Solutions business. About 90 Appro employees join the company as part of the buy. Cray said that Daniel Kim, the CEO of Appro, will head up its new Cluster Solutions business. Appro was founded in 1991.