Stratus Computer, a maker of high-end computers with redundant components to better withstand hardware failure, has upgraded its Continuum line with the latest processors from Hewlett-Packard. The single-processor Continuum 652-2 and dual-processor 1252-2 now use HP's PA-8600 chip, giving the machines as much as 33 percent more speed compared with PA-8500 models, the company said. The cheapest such system costs $284,000. Stratus also is at work on a Windows computer that uses Intel chips that is expected to be less expensive.