VAXft

The VAXft was a family of fault-tolerant minicomputers developed and manufactured by Digital Equipment Corporation (DEC) using processors implementing the VAX instruction set architecture (ISA). "VAXft" stood for "Virtual Address Extension, fault tolerant". These systems ran the OpenVMS operating system, and were first supported by VMS 5.4. Two layered software products, VAXft System Services and VMS Volume Shadowing, were required to support the fault-tolerant features of the VAXft and for the redundancy of data stored on hard disk drives.

All VAXft systems shared the same basic system architecture. A VAXft system consisted of two "zones" that operated in lock-step: "Zone A" and "Zone B". Each zone was a fully functional computer, capable of running an operating system, and was identical to the other in hardware configuration. Lock-step was achieved by hardware on the CPU module. The CPU module of each zone was connected to the other with a crosslink cable. The crosslink cables carried the results of instructions executed by one CPU module to the other, where they were compared by hardware with the results of the same instructions executed by the latter to ensure that they were identical. The two zones were kept synchronous by a clock signal carried by the crosslink cables. When a hardware failure occurred in one of the zones, the affected zone was brought offline without bringing down the other zone, which continued to operate as normal. When repairs were completed, the offline zone was powered on and automatically resynchronized with the other zone, restoring redundancy.

The VAXft Model 310, introduced as the VAXft 3000 Model 310, code named "Cirrus", was introduced in February 1990 and shipped in June. It was the first VAXft model, and was DEC's first fault-tolerant computer that was generally available. At the 1991 launch of new VAXft models, the VAX 3000 Model 310 was renamed to follow the new naming scheme, becoming the VAXft Model 310. The Model 310 had a theoretical maximum performance of 3.8 VUPs.

When announced, the Model 310 had a starting price of US$200,000. In August 1990, slow sales prompted DEC to reduce the US price of the Model 310 to US$168,000.

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