By the end of next year, United States Department of Energy researchers hope to build a new computer powerful enough to engage in virtual nuclear explosions so realistic that real-world bomb tests could become obsolete. The computer-development project responds to President Bill Clinton's call for a "science-based stockpile stewardship program" to maintain a safe, secure, and reliable nuclear deterrent without underground testing. Key to the proposed simulation approach to testing will be creation of a so-called teraflops computer-"tera" meaning 1 trillion, and "flops" meaning floating point operations per second-a massively parallel supercomputer much faster than any in existence today. The fastest computing speed to date is 281 gigaflops-"giga" meaning 1 billion-whereas the new computer will aim for 1.8 teraflops. Santa Clara, Calif.-based Intel Corp. will provide thousands of P6 microprocessors-the successor chip to its Pentium chip-for the $46 million project, which will involve the Sandia, Los Alamos, and Lawrence Livermore...