Tandem Computers, Inc. was the dominant manufacturer of
fault-tolerant computer system
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...
s for
ATM networks,
bank
A bank is a financial institution that accepts deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital markets.
Because ...
s,
stock exchange
A stock exchange, securities exchange, or bourse is an exchange where stockbrokers and traders can buy and sell securities, such as shares of stock, bonds and other financial instruments. Stock exchanges may also provide facilities for th ...
s, telephone switching centers, and other similar commercial
transaction processing
Transaction processing is information processing in computer science that is divided into individual, indivisible operations called ''transactions''. Each transaction must succeed or fail as a complete unit; it can never be only partially comple ...
applications requiring maximum uptime and zero data loss. The company was founded by
Jimmy Treybig
James G. Treybig is the founder of Tandem Computers, which designed and manufactured the first fault tolerant computers, in 1974. These pioneering computers were marketed to transaction processing customers, who used them for Automatic teller machi ...
in 1974 in
Cupertino, California
Cupertino ( ) is a city in Santa Clara County, California, United States, directly west of San Jose on the western edge of the Santa Clara Valley with portions extending into the foothills of the Santa Cruz Mountains. The population was 57,8 ...
. It remained independent until 1997, when it became a server division within
Compaq
Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...
. It is now a server division within
Hewlett Packard Enterprise
The Hewlett Packard Enterprise Company (HPE) is an American multinational information technology company based in Spring, Texas, United States.
HPE was founded on November 1, 2015, in Palo Alto, California, as part of the splitting of the H ...
, following
Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
's acquisition of Compaq and the split of Hewlett Packard into
HP Inc.
HP Inc. is an American multinational information technology company headquartered in Palo Alto, California, that develops personal computers (PCs), printers and related supplies, as well as 3D printing solutions.
It was formed on November ...
and Hewlett Packard Enterprise.
Tandem's
NonStop systems use a number of independent identical processors and redundant storage devices and controllers to provide automatic high-speed "
failover
Failover is switching to a redundant or standby computer server, system, hardware component or network upon the failure or abnormal termination of the previously active application, server, system, hardware component, or network in a computer net ...
" in the case of a hardware or software failure. To contain the scope of failures and of corrupted data, these multi-computer systems have no shared central components, not even main memory. Conventional multi-computer systems all use shared memories and work directly on shared data objects. Instead, NonStop processors cooperate by exchanging messages across a reliable fabric, and software takes periodic snapshots for possible rollback of program memory state.
Besides handling failures well, this "
shared-nothing A shared-nothing architecture (SN) is a distributed computing architecture in which each update request is satisfied by a single node (processor/memory/storage unit) in a computer cluster. The intent is to eliminate contention among nodes. Nodes do ...
" messaging system design also scales extremely well to the largest commercial workloads. Each doubling of the total number of processors would double system throughput, up to the maximum configuration of 4000 processors. In contrast, the performance of conventional multiprocessor systems is limited by the speed of some shared memory, bus, or switch. Adding more than 4–8 processors in that manner gives no further system speedup. NonStop systems have more often been bought to meet scaling requirements than for extreme fault tolerance. They compete well against IBM's largest mainframes, despite being built from simpler minicomputer technology.
Founding
Tandem Computers was founded in 1974 by
James Treybig
James G. Treybig is the founder of Tandem Computers, which designed and manufactured the first fault tolerant computers, in 1974. These pioneering computers were marketed to transaction processing customers, who used them for ATMs, banks, stock ex ...
. Treybig first saw the market need for fault tolerance in OLTP (online transaction processing) systems while running a marketing team for
Hewlett Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
's
HP 3000
The HP 3000 series is a family of 16-bit and 32-bit minicomputers from Hewlett-Packard. It was designed to be the first minicomputer with full support for time-sharing in the hardware and the operating system, features that had mostly been limite ...
computer division, but HP was not interested in developing for this niche. He then joined the venture capital firm
Kleiner & Perkins and developed the Tandem business plan there. Treybig pulled together a core engineering team hired away from the
HP 3000
The HP 3000 series is a family of 16-bit and 32-bit minicomputers from Hewlett-Packard. It was designed to be the first minicomputer with full support for time-sharing in the hardware and the operating system, features that had mostly been limite ...
division: Mike Green, Jim Katzman, Dave Mackie and Jack Loustaunou. Their business plan called for ultra-reliable systems that never had outages and never lost or corrupted data. These were modular in a new way that was safe from all "
single-point failure
A single point of failure (SPOF) is a part of a system that, if it fails, will stop the entire system from working. SPOFs are undesirable in any system with a goal of high availability or reliability, be it a business practice, software appl ...
s", yet would be only marginally more expensive than conventional non-fault-tolerant systems. They would be less expensive and support more throughput than some existing ad-hoc toughened systems that used redundant but usually required "hot spares".
Each engineer was confident they could quickly pull off their own part of this tricky new design, but doubted that others' areas could be worked out. The parts of the hardware and software design that did not have to be different were largely based on incremental improvements to the familiar hardware and software designs of the HP 3000. Many subsequent engineers and programmers also came from HP. Tandem headquarters in
Cupertino, California
Cupertino ( ) is a city in Santa Clara County, California, United States, directly west of San Jose on the western edge of the Santa Clara Valley with portions extending into the foothills of the Santa Cruz Mountains. The population was 57,8 ...
, were a quarter mile away from the HP offices. Initial venture capital investment in Tandem Computers came from Tom Perkins, who was formerly a general manager of the HP 3000 division.
The business plan included detailed ideas for building a unique corporate culture reflecting Treybig's values.
The design of the initial ''Tandem/16'' hardware was completed in 1975 and the first system shipped to Citibank in May 1976.
The company enjoyed uninterrupted exponential growth up through 1983. ''
Inc.'' magazine ranked Tandem as the fastest-growing public company in America. By 1996, Tandem was a $2.3 billion company employing approximately 8,000 people worldwide.
Tandem NonStop (TNS) stack machines
Over 40 years, Tandem's main
NonStop product line has grown and evolved in an upward-compatible way from the initial T/16 fault-tolerant system, with three major changes to date to its top-level modular architecture or its programming-level instruction set architecture. Within each series, there have been several major re-implementations as chip technology progressed.
While conventional systems of the era, including large
mainframes
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...
, had mean-time-between-failures (MTBF) on the order of a few days, the NonStop system was designed to failure intervals 100 times longer, with
uptime
Uptime is a measure of system reliability, expressed as the percentage of time a machine, typically a computer, has been working and available. Uptime is the opposite of downtime.
It is often used as a measure of computer operating system reliabi ...
s measured in years. Nevertheless, the NonStop was designed to be price-competitive with conventional systems, with a simple 2-CPU system priced at just over twice that of a competing single-processor mainframe, as opposed to four or more times of other fault-tolerant solutions.
Nonstop I
The first system was the Tandem/16 or T/16, later re-branded NonStop I. The machine consisted of between two and 16 CPUs, organized as a fault-tolerant
computer cluster
A computer cluster is a set of computers that work together so that they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software.
The comp ...
packaged in a single rack. Each CPU had its own private, unshared memory, its own
I/O processor, its own private I/O bus to connect to I/O controllers, and dual connections to all the other CPUs over a custom inter-CPU backplane
bus
A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
called Dynabus. Each disk controller or network controller was duplicated and had dual connections to both CPUs and devices. Each disk was mirrored, with separate connections to two independent disk controllers. If a disk failed, its data was still available from its mirrored copy. If a CPU or controller or bus failed, the disk was still reachable through alternative CPU, controller, and/or bus. Each disk or network controller was connected to two independent CPUs. Power supplies were each wired to only one side of some pair of CPUs, controllers, or buses, so that the system would keep running well without loss of connections if one power supply failed. The careful complex arrangement of parts and connections in customers' larger configurations were documented in a Mackie diagram, named after lead salesman David Mackie who invented the notation.
None of these duplicated parts were wasted "hot spares"; everything added to system throughput during normal operations.
Besides recovering well from failed parts, the T/16 was also designed to detect as many kinds of intermittent failures as possible, as soon as possible. This prompt detection is called "fail fast". The point was to find and isolate corrupted data before it was permanently written into databases and other disk files. In the T/16, error detection was by some added custom circuits that added little cost to the total design; no major parts were duplicated just to get error detection.
![TANDEM T16 Memory](https://upload.wikimedia.org/wikipedia/commons/d/d4/TANDEM_T16_Memory.jpg)
The T/16 CPU was a proprietary design. It was greatly influenced by the
HP 3000
The HP 3000 series is a family of 16-bit and 32-bit minicomputers from Hewlett-Packard. It was designed to be the first minicomputer with full support for time-sharing in the hardware and the operating system, features that had mostly been limite ...
minicomputer. They were both
microprogrammed,
16-bit
16-bit microcomputers are microcomputers that use 16-bit microprocessors.
A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...
,
stack-based machines with segmented,
16-bit
16-bit microcomputers are microcomputers that use 16-bit microprocessors.
A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...
virtual addressing. Both were intended to be programmed exclusively in high-level languages, with no use of
assembler
Assembler may refer to:
Arts and media
* Nobukazu Takemura, avant-garde electronic musician, stage name Assembler
* Assemblers, a fictional race in the ''Star Wars'' universe
* Assemblers, an alternative name of the superhero group Champions of A ...
. Both were initially implemented via standard low-density
TTL
TTL may refer to:
Photography
* Through-the-lens metering, a camera feature
* Zenit TTL, an SLR film camera named for its TTL metering capability
Technology
* Time to live, a computer data lifespan-limiting mechanism
* Transistor–transistor lo ...
chips, each holding a 4-bit slice of the 16-bit
ALU. Both had a small number of top-of-stack, 16-bit data registers plus some extra address registers for accessing the memory stack. Both used
Huffman encoding
In computer science and information theory, a Huffman code is a particular type of optimal prefix code that is commonly used for lossless data compression. The process of finding or using such a code proceeds by means of Huffman coding, an algori ...
of operand address offsets, to fit a large variety of address modes and offset sizes into the 16-bit instruction format with very good code density. Both relied heavily on pools of indirect addresses to overcome the short instruction format. Both supported larger 32- and 64-bit operands via multiple ALU cycles, and memory-to-memory string operations. Both used "big-endian" addressing of long versus short memory operands. These features had all been inspired by Burroughs B5500-B6800 mainframe stack machines.
The T/16 instruction set changed several features from the HP 3000 design. The T/16 supported paged virtual memory from the beginning. The HP 3000 series did not add paging until the PA-RISC generation, 10 years later (although MPE V it had a form of paging via the APL firmware, in 1978). Tandem added support for 32-bit addressing in its second machine; HP 3000 lacked this until its PA-RISC generation. Paging and long addresses was critical for supporting complex system software and large applications. The T/16 treated its top-of-stack registers in a novel way; the compiler, not the microcode, was responsible for deciding when full registers were spilled to the memory stack and when empty registers were re-filled from the memory stack. On the HP 3000, this decision took extra microcode cycles in every instruction. The HP 3000 supported
COBOL
COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily us ...
with several instructions for calculating directly on arbitrary-length BCD (binary-coded decimal) strings of digits. The T/16 simplified this to single instructions for converting between BCD strings and 64-bit binary integers.
In the T/16, each CPU consisted of two boards of TTL logic and
SRAMs, and ran at about 0.7
MIPS. At any instant, it could access only four virtual memory segments (System Data, System Code, User Data, User Code), each limited to 128 kB in size. The 16-bit address spaces were already too small for major applications when it shipped.
The first release of T/16 had only a single programming language,
Transaction Application Language Transaction Application Language or TAL (originally "Tandem Application Language") is a block-structured, procedural language optimized for use on Tandem Computers, Tandem hardware. TAL resembles a cross between C (programming language), C and Pasca ...
(TAL). This was an efficient machine-dependent systems programming language (for operating systems, compilers, etc.) but could also be used for non-portable applications. It was derived from HP 3000's System Programming Language (SPL). Both had semantics similar to
C but a syntax based on Burroughs'
ALGOL
ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...
. Subsequent releases added support for Cobol74,
Fortran, and
MUMPS
MUMPS ("Massachusetts General Hospital Utility Multi-Programming System"), or M, is an imperative, high-level programming language with an integrated transaction processing key–value database. It was originally developed at Massachusetts Gener ...
.
The Tandem
NonStop series ran a custom
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
which was significantly different from Unix or HP 3000's MPE. It was initially called T/TOS (Tandem Transactional Operating System) but soon named Guardian for its ability to protect all data from machine faults or software faults. In contrast to all other commercial operating systems, Guardian was based on message passing as the basic way for all processes to interact, without shared memory, regardless of where the processes were running. This approach easily scaled to multiple-computer clusters and helped isolate corrupted data before it propagated.
All file system processes and all transactional application processes were structured as master/slave pairs of processes running in separate CPUs. The slave process periodically took snapshots of the master's memory state, and took over the workload if and when the master process ran into trouble. This allowed the application to survive failures in any CPU or its associated devices, without data loss. It further allowed recovery from some intermittent-style software failures. Between failures, the monitoring by the slave process added some performance overhead but this was far less than the 100% duplication in other system designs. 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.
NonStop II
In 1981, all T/16 CPUs were replaced by the NonStop II. Its main difference from the T/16 was support for occasional 32-bit addressing via a user-switchable "extended data segment". This supported the next ten years of growth in software and was a huge advantage over the T/16 or HP 3000. Unfortunately, visible registers remained 16-bit, and this unplanned addition to the instruction set required executing many instructions per memory reference compared to most 32-bit minicomputers. All subsequent TNS computers were hampered by this instruction set inefficiency. Also, the NonStop II lacked wider internal data paths and so required additional microcode steps for 32-bit addresses. A NonStop II CPU had three boards, using chips and design similar to the T/16. The NonStop II also replaced core memory with battery-backed DRAM memory.
NonStop TXP
In 1983, the NonStop TXP CPU was the first entirely new implementation of the TNS instruction set architecture. It was built from standard TTL chips and Programmed Array Logic chips, with four boards per CPU module. It had Tandem's first use of cache memory. It had a more direct implementation of 32-bit addressing, but still sent them through 16-bit adders. A wider microcode store allowed a major reduction in the cycles executed per instruction; speed increased to 2.0 MIPS. It used the same rack packaging, controllers, backplane, and buses as before. The Dynabus and I/O buses had been overdesigned in the T/16 so they would work for several generations of upgrades.
FOX
Up to 14 TXP and NonStop II systems could now be combined via FOX, a long-distance fault-tolerant
fibre optic
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...
bus for connecting TNS clusters across a business campus; a cluster of clusters with a total of 224 CPUs. This allowed further scale-up for taking on the largest mainframe applications. Like the CPU modules within the computers, Guardian could failover entire task sets to other machines in the network. Worldwide clusters of 4000 CPUs could also be built via conventional long-haul network links.
NonStop VLX
In 1986, Tandem introduced a third generation CPU, the NonStop VLX. It had 32-bit datapaths, wider microcode, 12 MHz cycle time, and a peak rate of one instruction per microcycle. It was built from three boards of ECL gate array chips (with TTL pinout). It had a revised Dynabus with speed raised to 20 Mbytes/sec per link, 40 Mbytes/sec total. FOX II increased the physical diameter of TNS clusters to 4 kilometers.
Tandem's initial database support was only for hierarchical, non-relational databases via the
ENSCRIBE
Enscribe is the native hierarchical database
A hierarchical database model is a data model in which the data are organized into a tree-like structure. The data are stored as records which are connected to one another through links. A record is a c ...
file system. This was extended into a relational database called ENCOMPASS. In 1986 Tandem introduced the first fault-tolerant
SQL database,
NonStop SQL NonStop SQL is a commercial relational database management system that is designed for fault tolerance and scalability, currently offered by Hewlett Packard Enterprise. The latest version is SQL/MX 3.4.
The product was originally developed by Tan ...
. Developed totally in-house, NonStop SQL includes a number of features based on Guardian to ensure
data validity across nodes. NonStop SQL is famous for
scaling linearly in
performance
A performance is an act of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function.
Management science
In the work place ...
with the number of nodes added to the system, whereas most databases had performance that plateaued quite quickly, often after just two CPUs. A later version released in 1989 added transactions that could be spread over nodes, a feature that remained unique for some time. NonStop SQL continued to evolve, first as SQL/MP and then SQL/MX, which transitioned from Tandem to Compaq to HP. The code remains in use in both HP's SQL/MX and the Apache
Trafodion project.
NonStop CLX
In 1987 Tandem introduced the NonStop CLX, a low-cost less-expandable minicomputer system. Its role was for growing the low end of the fault-tolerant market, and for deploying on the remote edges of large Tandem networks. Its initial performance was roughly similar to the TXP; later versions were about 20% slower than a VLX. Its small cabinet could be installed into any "copier room" office environment. A CLX CPU was one board, containing six "compiled silicon" ASIC CMOS chips. The CPU core chip was duplicated and lock stepped for maximal error detection. Pinout was a main limitation of this chip technology. Microcode, cache, and TLB were all external to the CPU core and shared a single bus and single SRAM memory bank. As a result, CLX required at least two machine cycles per instruction.
NonStop Cyclone
In 1989 Tandem introduced the NonStop Cyclone, a fast but expensive system for the mainframe end of the market. Each self-checking CPU took three boards full of hot-running ECL gate array chips, plus memory boards. Despite being microprogrammed, the CPU was
superscalar
A superscalar processor is a CPU that implements a form of parallelism called instruction-level parallelism within a single processor. In contrast to a scalar processor, which can execute at most one single instruction per clock cycle, a sup ...
, often completing two instructions per cache cycle. This was accomplished by having a separate microcode routine for every common pair of instructions. That fused pair of stack instructions generally accomplished the same work as a single instruction of normal 32-bit minicomputers. Cyclone processors were packaged as sections of four CPUs each, and the sections joined by a fiber optic version of Dynabus.
Like Tandem's prior high-end machines, Cyclone cabinets were styled with much angular black to suggest strength and power. Advertising videos directly compared Cyclone to the
Lockheed SR-71 Blackbird
The Lockheed SR-71 "Blackbird" is a long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft developed and manufactured by the American aerospace company Lockheed Corporation. It was operated by the United States Air Force ...
Mach 3 spy plane. Cyclone's name was supposed to represent its unstoppable speed in roaring through OLTP workloads. Announcement day was October 17 and the press came to town. That afternoon, the region was struck by the magnitude 6.9
Loma Prieta earthquake
The 1989 Loma Prieta earthquake occurred on California's Central Coast on October 17 at local time. The shock was centered in The Forest of Nisene Marks State Park in Santa Cruz County, approximately northeast of Santa Cruz on a section of t ...
, causing freeway collapses in
Oakland
Oakland is the largest city and the county seat of Alameda County, California, United States. A major West Coast port, Oakland is the largest city in the East Bay region of the San Francisco Bay Area, the third largest city overall in the Bay A ...
and major fires in
San Francisco
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
. Tandem offices were shaken, but no one was badly hurt on site. This was the first and last time that Tandem named its products after a natural disaster.
Other product lines
Rainbow
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. Rainbow's hardware was a 32-bit register-file machine that aimed to be better than a VAX. For reliable programming, the main programming language was "TPL", a subset of Ada. At that time, people barely understood how to compile Ada to unoptimized code. There was no migration path for existing NonStop system software coded in TAL. The OS and database and Cobol compilers were entirely redesigned. Customers would see it as a totally disjoint product line requiring all-new software from them. The software side of this ambitious project took much longer than planned. The hardware was already obsolete and out-performed by TXP before its software was ready, so the Rainbow project was abandoned. All subsequent efforts emphasized upward compatibility and easy migration paths.
Development of Rainbow's advanced client/server application development framework called "Crystal" continued awhile longer and was spun off as the "Ellipse" product of Cooperative Systems Inc.
Dynamite PC
In 1985, Tandem attempted to grab a piece of the rapidly growing
personal computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
market with its introduction of the
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
based Dynamite PC/workstation. Sadly, 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. It was quietly and quickly withdrawn from the market.
Integrity
Tandem's message-based NonStop operating system had advantages for scaling, extreme reliability, and efficiently using expensive "spare" resources. But many potential customers wanted just good-enough reliability in a small system, using a familiar Unix operating system and industry-standard programs. 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. The most successful competitor was
Stratus Technologies
Stratus Technologies, Inc. is a major producer of fault tolerant computer servers and software. The company was founded in 1980 as Stratus Computer, Inc. in Natick, Massachusetts, and adopted its present name in 1999. The current CEO and preside ...
, whose machines were re-marketed by IBM as "IBM System/88".
In such systems, the spare processors do not contribute to system throughput between failures, but merely redundantly execute exactly the same data thread as the active processor at the same instant, in "lock step". Faults are detected by seeing when the cloned processors' outputs diverged. To detect failures, the system must have two physical processors for each logical, active processor. To also implement automatic failover recovery, the system must have three or four physical processors for each logical processor. The triple or quadruple cost of this sparing is practical when the duplicated parts are commodity single-chip microprocessors.
Tandem's products for this market began with the
Integrity
Integrity is the practice of being honest and showing a consistent and uncompromising adherence to strong moral and ethical principles and values.
In ethics, integrity is regarded as the honesty and truthfulness or accuracy of one's actions. Inte ...
line in 1989, using MIPS processors and a "NonStop UX" variant of Unix. It was developed in Austin TX. 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. Their fast clocks could not be synchronized as in strict lock stepping, so voting instead happened at each interrupt. Some other version of Integrity used 4x "pair and spares" redundancy. Pairs of processors ran in lock-step to check each other. When they disagreed, both processors were marked untrusted and their workload was taken over by a hot-spare pair of processors whose state was already current. In 1995, the Integrity S4000 was the first to use ServerNet and moved toward sharing peripherals with the NonStop line.
Wolfpack
In 1995–1997, Tandem partnered with Microsoft to implement high-availability features and advanced SQL configurations in clusters of commodity Windows NT machines. This project was called "Wolfpack" and first shipped as
Microsoft Cluster Server
Microsoft Cluster Server (MSCS) is a computer program that allows server computers to work together as a computer cluster, to provide failover and increased availability of applications, or parallel calculating power in case of high-performan ...
in 1997. Microsoft benefited greatly from this partnership; Tandem did not.
TNS/R NonStop migration to MIPS
When Tandem was formed in 1974, every computer company had to design and build its CPUs from basic circuits, using its own proprietary instruction set and own 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 much cheaper as a result. But it became increasingly expensive for a computer company to design those advanced custom chips, or build the plants to fabricate the chips. Facing the challenges of this rapidly changing marketplace and manufacturing landscape, Tandem chose to partner with
MIPS and adopted its
R3000
The R3000 is a 32-bit RISC microprocessor chipset developed by MIPS Computer Systems that implemented the MIPS I instruction set architecture (ISA). Introduced in June 1988, it was the second MIPS implementation, succeeding the R2000 as the flags ...
and successor chipsets and their advanced optimizing compiler. Subsequent NonStop Guardian machines using the
MIPS architecture
MIPS (Microprocessor without Interlocked Pipelined Stages) is a family of reduced instruction set computer (RISC) instruction set architectures (ISA)Price, Charles (September 1995). ''MIPS IV Instruction Set'' (Revision 3.2), MIPS Technologies, ...
were known to programmers as TNS/R machines, but had a variety of marketing names.
Cyclone/R
In 1991, Tandem released the Cyclone/R, also known as CLX/R. This was a low cost mid-range system based on CLX components, but used R3000 microprocessors instead of the much slower CLX stack machine board. To minimize time to market, this machine was initially shipped without any MIPS native-mode software. Everything, including its NSK operating system and SQL database, was compiled to TNS stack machine code. That object code was then translated to equivalent partially optimized MIPS instruction sequences at kernel install time by a tool called the Accelerator. Less-important programs could also be executed directly without pre-translation, via a TNS code
interpreter. These migration techniques were very successful and are still in use today. Everyone's software was brought over without extra work, and the performance was good enough for mid-range machines, and programmers could ignore the instruction differences, even when debugging at machine code level. These Cyclone/R machines were updated with a faster native-mode NSK in a follow-up release.
The R3000 and later microprocessors had only a typical amount of internal error checking, insufficient for Tandem's needs. So the Cyclone/R ran pairs of R3000 processors in lock step, running the same data thread. It used a curious variation of lock stepping. The checker processor ran 1 cycle behind the primary processor. This allowed them to share a single copy of external code and data caches without putting excessive pinout load on the sysbus and lowering the system clock rate. To successfully run microprocessors in lock step, the chips must be designed to be fully deterministic. Any hidden internal state must be cleared by the chip's reset mechanism. Otherwise, the matched chips will sometimes get out of sync for no visible reason and without any faults, long after the chips are restarted. All chip designers agree that these are good principles because it helps them test chips at manufacturing time. But all new microprocessor chips seemed to have bugs in this area, and required months of shared work between MIPS and Tandem to eliminate or work around the final subtle bugs.
NonStop Himalaya K-series
In 1993, Tandem released the NonStop Himalaya K-series with the faster MIPS
R4400
The R4000 is a microprocessor developed by MIPS Computer Systems that implements the MIPS III instruction set architecture (ISA). Officially announced on 1 October 1991, it was one of the first 64-bit microprocessors and the first MIPS III impleme ...
, a native mode NSK, and fully expandable Cyclone system components. These were still connected by Dynabus, Dynabus+, and the original I/O bus, which by now were all running out of performance headroom.
Open System Services
In 1995, the NonStop Kernel was extended with a Unix-like
POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
environment called Open System Services. The original Guardian shell and ABI remained available.
NonStop Himalaya S-Series
In 1997 Tandem introduced the NonStop Himalaya S-Series with a new top-level system architecture based on
ServerNet connections. ServerNet replaced the obsolete Dynabus, FOX, and I/O buses. It was much faster, more general, and could be extended to more than just two-way redundancy via an arbitrary fabric of point-to-point connections. Tandem designed ServerNet for its own needs but then promoted its use by others; it evolved into the
InfiniBand
InfiniBand (IB) is a computer networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used ...
industry standard.
All S-Series machines used MIPS processors, including the R4400,
R10000
The R10000, code-named "T5", is a RISC microprocessor implementation of the MIPS IV instruction set architecture (ISA) developed by MIPS Technologies, Inc. (MTI), then a division of Silicon Graphics, Inc. (SGI). The chief designers are Chris Rowe ...
, R12000, and R14000.
The design of the later, faster MIPS cores was primarily funded by Silicon Graphics Inc. But Intel's Pentium Pro overtook the performance of RISC designs and also SGI's graphics business shrunk. After the R10000, there was no investment in significant new MIPS core designs for high-end servers. So Tandem needed to eventually move its NonStop product line yet again onto some other microprocessor architecture with competitive fast chips.
Acquisition by Compaq, attempted migration to Alpha
Jimmy Treybig remained CEO of the company he founded until a downturn in 1996. The next CEO was Roel Pieper, who joined the company in 1996 as president and CEO. Re-branding to promote itself as a true Wintel (Windows/Intel) platform was conducted by their in-house brand and creative team led by Ronald May, who later went on to co-found the Silicon Valley Brand Forum in 1999. The concept worked, and shortly thereafter the company was acquired by Compaq.
Compaq
Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...
's x86-based server division was an early outside adopter of Tandem's ServerNet/Infiniband interconnect technology. In 1997, Compaq acquired the Tandem Computers company and NonStop customer base to balance Compaq's heavy focus on low-end PCs. In 1998, Compaq also acquired the much larger
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...
and inherited its
DEC Alpha
Alpha (original name Alpha AXP) is a 64-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace 32-bit VAX complex instruction set computers ...
RISC servers with
OpenVMS
OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...
and
Tru64 Unix
Tru64 UNIX is a discontinued 64-bit UNIX operating system for the Alpha instruction set architecture (ISA), currently owned by Hewlett-Packard (HP). Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation ( ...
customer bases. Tandem was then midway in porting its NonStop product line from MIPS R12000 microprocessors to Intel's new
Itanium
Itanium ( ) is a discontinued family of 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Launched in June 2001, Intel marketed the processors for enterprise servers and high-performance computin ...
Merced microprocessors. This project was restarted with Alpha as the new target to align NonStop with Compaq's other large server lines. But in 2001, Compaq terminated all Alpha engineering investments in favor of the Itanium microprocessors.
Acquisition by Hewlett Packard, TNS/E migration to Itanium
In 2001,
Hewlett Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
similarly made the choice to abdicate its successful
PA-RISC
PA-RISC is an instruction set architecture (ISA) developed by Hewlett-Packard. As the name implies, it is a reduced instruction set computer (RISC) architecture, where the PA stands for Precision Architecture. The design is also referred to as ...
product lines in favor of Intel's Itanium microprocessors that HP helped to design. Shortly thereafter, Compaq and HP announced their plan to merge and consolidate their similar product lines. This contentious merger became official in May 2002. 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.
In some ways, Tandem's journey from HP-inspired start-up, to an HP-inspired competitor, then to an HP division was "bringing Tandem back to its original roots", but this was definitely not the same HP.
The re-port of the NSK-based NonStop product line from MIPS processors to Itanium-based processors was finally completed and is branded as "HP Integrity NonStop Servers". (This NSK Integrity NonStop is unrelated to Tandem's original "Integrity" series for Unix.)
Because it was not possible to run Itanium McKinley chips with clock-level lock stepping, the Integrity NonStop machines instead use comparisons between chip states at longer time scales, at interrupt points and at various software sync points in between interrupts. The intermediate sync points are automatically triggered at every n'th taken branch instruction, and are also explicitly inserted into long loop bodies by all NonStop compilers. The machine design supports both dual and triple redundancy, with either two or three physical microprocessors per logical Itanium processor. The triple version is sold to customers needing the utmost reliability. This new checking approach is called NSAA, NonStop Advanced Architecture.
As in the earlier migration from stack machines to MIPS microprocessors, all customer software was carried forward without source changes. "Native mode" source code compiled directly to MIPS machine code was simply recompiled for Itanium. Some older "non native" software was still in TNS stack machine form. These were automatically ported onto Itanium via object code translation techniques.
Itanium migration to Intel X86
The people working for Tandem/HP have a long history of porting the kernel onto new hardware. The latest endeavor was to move from Itanium to the Intel x86 architecture. It was completed in 2014 with the first systems already being commercially available.
The inclusion of the fault-tolerant 4X FDR (Fourteen Data Rate) InfiniBand double-wide switches provides more than a 25 times increase in system interconnect capacity for responding to business growth.
Outlook, other
NSK Guardian also became the base for the HP Neoview OS, the operating system used in the
HP Neoview systems that were tailored for use in Business Intelligence and Enterprise Data Warehouse use. NonStop SQL/MX was also the starting point for Neoview SQL, which was tailored to Business Intelligence use. The code was also ported to Linux and served as the basis for the Apache
Trafodion project.
Corporate culture
Treybig’s business plan included detailed ideas for building a corporate culture reflecting Treybig's values, such as paid six week sabbaticals each 4 years for all employees, an annual gift of 100 shares of Tandem stock to all employees, a weekly all-employee party known as Beer Bust Fridays, and a world-wide closed circuit monthly telecast ("First Friday") to keep employees informed.
The headquarters office also had an outdoor basketball court and a swimming pool manned by a lifeguard. Employees and their families were welcome to use it. It was full of kids on the weekends.
User groups
*
ITUG
The Connect User Community is a 501(c)(6) nonprofit association, an independent user community for Hewlett Packard Enterprise (HPE).
Connect is a group of more than 70,000 HP customers, partners and employees. It resulted from the merger in May, ...
(
International Tandem User Group) now part of
Connect (users group)
The Connect User Community is a 501(c)(6) nonprofit association, an independent user community for Hewlett Packard Enterprise (HPE).
Connect is a group of more than 70,000 HP customers, partners and employees. It resulted from the merger in May, ...
* OzTUG The Australia and New Zealand Tandem Users Group here:
OzTUG at LinkedInBITUG (British Isles NonStop (Tandem) User Group)
See also
*
Jim Gray (computer scientist)
James Nicholas Gray (1944 – declared dead in absentia 2012) was an American computer scientist who received the Turing Award in 1998 "for seminal contributions to database and transaction processing research and technical leadership in system im ...
*
NonStop
*
Stratus Technologies
Stratus Technologies, Inc. is a major producer of fault tolerant computer servers and software. The company was founded in 1980 as Stratus Computer, Inc. in Natick, Massachusetts, and adopted its present name in 1999. The current CEO and preside ...
References
External links
{{Commons category, Tandem Computers
NonStop Computing Homenbsp;— the main Nonstop Computing page at HP
NonStop for Dummiesnbsp; - a short booklet introducing the NonStop computing platform, 2014
Tandem Technical Reportsnbsp;— a page at HP with a number of Tandem white papers
Tandem Systems Reviewnbsp;— PDFs 1983–1994
Tandem Computers Unpluggednbsp; - a book focusing on the company history, 2014
Fault-tolerant computer systems
Defunct computer hardware companies
Defunct computer companies based in California
Minicomputers
Transaction processing
Technology companies based in the San Francisco Bay Area
Companies based in Cupertino, California
American companies established in 1974
Computer companies established in 1974
Computer companies disestablished in 1997
1974 establishments in California
1997 disestablishments in California
Defunct companies based in the San Francisco Bay Area
Private equity portfolio companies
Hewlett-Packard acquisitions
1997 mergers and acquisitions