Tandem Computers Inc’s cautious entry into the Unix market with the sealed three-processor Integrity S2 MIPS Computer Systems Inc RISC-based machine was intended almost exclusively as a product for telephone companies, particularly ones whose AT&T Co 3B20D fault-tolerant machines were coming to the end of their useful life – but the company is finding unexpected interest in the machine from commercial accounts, Computerworld reports. It is therefore starting to discuss the machine with commercial users, although it insists that it is not as fault-tolerant as its proprietary Guardian-based machines. The S2 uses the voting system of fault-tolerance where all three processors operate in parallel on the same data and all is assumed to be well when all three come up with the same answer, soft errors are accomodated by taking the output from the two that agree, and when one processor consistantly gives results at variance with those of the other two, an alert is signalled, the processor is assumed to be faulty and is replaced. The machine thus delivers the performance of one CPU.
