Instead, NonStop processors cooperate by exchanging messages across a reliable fabric, and software takes periodic snapshots for possible rollback of program memory state.

[2][3][4] Treybig pulled together a core engineering team hired away from the HP 3000 division: Mike Green, Jim Katzman, Dave Mackie and Jack Loustaunou.

The business plan included detailed ideas for building a unique corporate culture reflecting Treybig's values.

The HP 3000 supported COBOL with several instructions for calculating directly on arbitrary-length BCD (binary-coded decimal) strings of digits.

The Tandem NonStop series ran a custom operating system which was significantly different from Unix or HP 3000's MPE.

Some major early applications were directly coded in this checkpoint style, but most instead used various Tandem software layers which hid the details of this in a semi-portable way.

A wider microcode store allowed a major reduction in the cycles executed per instruction; speed increased to 2.0 MIPS.

[13] Like the CPU modules within the computers, the Guardian operating system could failover entire task sets to other machines in the network.

[16] Developed totally in-house, NonStop SQL includes a number of features based on Guardian to ensure data validity across nodes.

[18][19] Its role was for growing the low end of the fault-tolerant market, and for deploying on the remote edges of large Tandem networks.

Like Tandem's prior high-end machines, Cyclone cabinets were styled with much angular black to suggest strength and power.

That afternoon, the region was struck by the magnitude 6.9 Loma Prieta earthquake, causing freeway collapses in Oakland and major fires in San Francisco.

In 1980–1983, Tandem attempted to re-design its entire hardware and software stack to put its NonStop methods on a stronger foundation than its inherited HP 3000 traits.

[23] In 1985, Tandem attempted to grab a piece of the rapidly growing personal computer market with its introduction of the MS-DOS based Dynamite PC/workstation.

Numerous design compromises (including a unique 8086-based hardware platform incompatible with expansion cards of the day and extremely limited compatibility with IBM-based PCs) relegated the Dynamite to serving primarily as a smart terminal.

Tandem's message-based NonStop operating system had advantages for scaling, extreme reliability, and efficiently using expensive "spare" resources.

Tandem's various fault-tolerant competitors all adopted a simpler hardware-only memory-centric design where all recovery was done by switching between hot spares.

Tandem's products for this market began with the Integrity line in 1989, using MIPS processors and a "NonStop UX" variant of Unix.

In 1991, the Integrity S2 used TMR, Triple Modular Redundancy, where each logical CPU used three MIPS R2000 microprocessors to execute the same data thread, with voting to find and lock out a failed part.

When Tandem was formed in 1974, every computer company designed and built its CPUs from basic circuits[citation needed], using its own proprietary instruction set, compilers, etc.

With each year of semiconductor progress with Moore's Law, more of a CPU's core circuits could fit into single chips and run faster and cheaper as a result.

Facing the challenges of this changing marketplace and manufacturing landscape, Tandem partnered with MIPS and adopted its R3000 and successor chipsets and their advanced optimizing compiler.

That object code was then translated to equivalent partially optimized MIPS instruction sequences at kernel install time by a tool called the Accelerator.

But Intel's sixth generation Pentium Pro overtook the performance of RISC designs, and also SGI's graphics business shrank.

In 1998, Compaq also acquired the much larger Digital Equipment Corporation and inherited its DEC Alpha RISC servers with OpenVMS and Tru64 Unix customer bases.

In 2001, Hewlett-Packard similarly made the choice to abdicate its successful PA-RISC product lines in favor of Intel's Itanium microprocessors that HP helped to design.

The consolidations were painful and destroyed the DEC and "HP Way" engineer-oriented cultures, but the combined company did know how to sell complex systems to enterprises and profit, so it was an improvement for the surviving NonStop division and its customers.

The intermediate synchronization points were automatically triggered at every n'th taken branch instruction and were also explicitly inserted into long loop bodies by all NonStop compilers.

[27] As in the earlier migration from stack machines to MIPS microprocessors, all customer software was carried forward without source changes.

The inclusion of the fault-tolerant 4X FDR (Fourteen Data Rate) InfiniBand double-wide switches provided more than 25 times increase in system interconnect capacity.