Rather than compromise the Unix System V kernel and thus the portability of Unix applications, Tandem Computers Inc has gone back to first principles in designing its new Integrity S2 fault-tolerant Unix system. In contrast to its proprietary NonStop systems, the three processor S2, built around the 16.7 MIPS Computer Systems Inc R2000 RISC but designed to move up with the R-series family, uses the voting system of fault-tolerance, where a comparator examines the results produced by the three processors. If a result from one differs from that from the other two, the latter are assumed to be correct, and the former is switched out. Diagnostic tests are run and if a fault is detected, alerts are given, if not, the error is assumed to have been a soft one and the processor is switched back in again. The S2 has duplicated memory and mirror disks, dual power system and dual-ported input-output subsystem. It is built around a proprietary fault-tolerant NonStop V+ bus compatible with the VMEbus: the bus interface module provides VMEbus controllers with paths to two separate NonStop V+ buses. The NonStop-UX operating system is based on System V.3, conforms to the System V Interface Definition, with added system recovery mechanisms, the Berkeley Fast File System and a memory management system designed to minimise memory-to-memory copies and maximise use of high-speed local memory. Tandem offers the X Window System, Network File System and TCP/IP and has adopted Oracle, Ingres and Informix relational databases, although it stresses that while it expects some users to want to run transaction processing applications on the S2, its primary offering for such applications will remain its proprietary NonStops under Guardian. The R2000 processors, each with its own clock, synchronised with that of the others, is rated at 11 MIPS to 12 MIPS. The Mass Storage Cabinet comes with two disks and a tape standard and is expandable to seven disks – or six and a tape drive. Each system can take up to four cabinets. S201, 202 and 204 configurations come with a 16-port asynchronous controller, S211, 212 and 214 come with Ethernet controllers. Primary target markets are telecommunications, the US Federal government and manufacturing. The S201 and S221 with duplicated 16Mb main memory, two 295Mb disks and a quarter inch tape drive cost from $172,000. The S202 and 212 take up to 40Mb memory and add a Mass Storage Cabinet with two more 295Mb disks at from UKP196,000; the S204 and 214 have SCSI channels for up to four disk cabinets and start at $248,000. NonStop-UX carries an initial licence fee of $12,000 then UKP400 a month. All are available now.
