Tolerant Systems was a company founded in 1983 by Eli Alon and Dale Shipely (both from Intel) to build fault-tolerant computer systems based on the idea of shoe-box building blocks.

Tolerant initially based their shoe-box system on the 32016 microprocessor from National Semiconductor, and then upgraded the systems to the 32032 when these true 32 bit processors became available. The shoe-box consisted of a OS processor and an I/O processor (both running under the 32K device. The OS processor ran a version of Unix called TX while the I/O processor ran a Real Time Executive developed by Tolerant.

Each shoe-box had two Ethernet connectors which allowed a fault-tolerant connection to other shoe-box systems. Further, a proprietary I/O system was created that ran at an amazing 3Mbyte/second up to 50 feet allowing up to 16 peripherals per I/O. Tolerant developed a custom Disk Controller, Communications Interface Processor (CIP), and Tape Controller that communicated on this I/O bus.

The CIP was a front-end for 12 or 16 serial ports also based on the National 32016 processor. The CIP could run forms software, or other pre-processing applications to allow intelligent use of the terminals that were attached.

The software gained a level of fault-tolerance through check-pointing technology. Applications needed to be fortified with this check-pointing to allow roll-back of the application on another processor if a hardware failure occurred.

Tolerant also developed a forerunner of today's RAID systems by incorporating a journaling file system and multiple copies or N-plexing the disk drive content.

The company got out of the hardware business in 1989 and became Veritas Software by using this earlier work in journaled file systems as the basis for a new line of products for NT and Unix systems.

Computer companies