Sequent Computer Systems, or Sequent, was a computer company that designed and manufactured multiprocessing computer systems. They were among the pioneers in high-performance symmetric multiprocessing (SMP) Open system (computing), innovating in both hardware (e.g. cache management and Interrupt handling) and software (e.g. read-copy-update).

Through a close partnership with Oracle Corporation that included the introduction of hardware and software optimizations, Sequent became a dominant high-end UNIX platform in the late 1980s and early 1990s. Later, after several corporate missteps, they returned to their roots, producing a next-generation high-end platform for UNIX and Windows NT based on a non-uniform memory access architecture, NUMA-Q.

As hardware prices fell in the late 1990s Sequent found their market shrinking, and eventually they were purchased by IBM in 1999.

The death knell for NUMA-Q and Sequent technology was sounded when in 2002, two layoffs at Sequent s former headquarters in Beaverton, Oregon ended all development on the systems for which IBM had acquired the company. According to a May 30, 2002 article in the Wall Street Journal (WSJ) entitled Sequent Deal Serves Hard Lesson for IBM : :When IBM bought Sequent, ...it [Sequent] lacked the size and resources to compete with Sun Microsystems and Hewlett-Packard in the Unix server market.... :In 1999, IBM had problems of its own with an aged and high-priced line of servers, particularly for its version of Unix known as AIX operating system. It also faced huge losses in personal computers and declining sales in its cash-cow Mainframe computer. Robert Stephenson, who headed the server group at IBM, saw acquiring Sequent as the best route to make IBM competitive in the market for large Unix servers where Sun was gobbling up market share.

When Stephenson retired shortly after IBM completed its acquisition of Sequent, responsibility for servers fell on Samuel J. Palmisano. The WSJ article noted that Palmisano wanted to simplify IBM s multipronged server strategy ; it also quoted Scott Gibson, one of two executives (along with Casey Powell) who led Sequent when it was founded. Gibson told the WSJ the acquisition was doomed because the guy who sponsored the acquisition retired.

Vestiges of Sequent s innovations live on in the form of data clustering software from PolyServe, various projects within OSDL, IBM contributions to the Linux kernel, and claims in the SCO v. IBM lawsuit.

= History =

Sequent formed in 1983 when a group of eighteen engineers and executives (including Gibson) left Intel after the failed Intel iAPX 432 mainframe on a chip project was cancelled. They started Sequent to develop a line of SMP computers, then considered one of the up-and-coming fields in computer design. Several engineers from AT&T Bell Labs also came over, bringing systems programming expertise.

Sequent s first computer systems were the Balance 8000 and Balance 21000 released in 1984. The Balance included up to 20 National Semiconductor NS32016 processors, each with a small cache connected to a common memory to form a shared memory system. The systems ran a modified version of Berkeley Software Distribution Unix they called DYNIX, for DYNamic unIX. The machines were designed to compete with the Digital Equipment Corporation VAX, with each of their inexpensive processors dedicated to a particular process. In addition the system included a series of libraries that could be used by programmers to develop applications that could use more than one processor at a time. The Balance systems were originally intended to be sold to OEMs as computing engines, but that market could not be developed. When the commercial market discovered their reliability and cost advantages, the company re-thought its marketing strategy. The Balance line sold well for three years to banks, the government, other commercial enterprises, and universities interested in parallel computing.

Their next series was the Intel 80386-based Symmetry, released in 1987. Various models supported between 2 and 30 processors, using a new write-back cache and a wider 64-bit Front side bus. 1991 s Symmetry 2000 models added SCSI drives, and were offered in versions with from one to six Intel 80486 processors. The next year they added the VMEbus based Symmetry 2000/x50 with faster CPUs.

The late 1980s and early 1990s saw big changes on the software side for Sequent. DYNIX was replaced by DYNIX/ptx, which was based on UNIX System V instead of BSD. And this was during a period when Sequent s high-end systems became particularly successful due to a close working relationship with Oracle Corporation, specifically Oracle database. In 1993 they added the Symmetry 2000/x90 along with their ptx/Cluster software, which added various High-availability cluster features and introduced custom support for Oracle Parallel Server.

In 1994 Sequent introduced the Symmetry 5000 series models SE20, SE60 and SE90, which used 66Mhz Pentium CPUs in systems from 2 to 30 processors. The next year they expanded that with the SE30/70/100 linup using 100MHz Pentiums, and then in 1996 with the SE40/80/120 with 166MHz Pentiums. With the addition of a VGA card and the Winserver NT software, the 5000 series could also run Windows NT.

Recognizing the increase in competition for SMP systems after having been early adopters of the architecture, Sequent sought its next source of differentiation. They licensed their technology to Intel to help commoditize the SMP market, and began investing in the development of a system based on a cache-coherent non-uniform memory architecture (ccNUMA). NUMA dedicates separate portions of memory to different processors, avoiding the bottleneck that occurs because only one processor can access memory at a time. Using NUMA would allow their multiprocessor machines to generally outperform SMP systems, at least when the tasks are tightly coupled with their memory — as is the case for servers, where each user tends to be looking at different files.

In 1996 they released the first of a new series of machines based on this new architecture. Known internally as STiNG, an Linux lawsuit.

In 2002, after Sun Microsystems began a public discussion of IBM s silence on their NUMA-based x430 system, IBM had a reduction-in-force, and announced that it had no further plans to market the x430 and would eventually drop support for the over 10,000 systems that Sequent and IBM had deployed.

= Detailed model descriptions =

The following is a more detailed description of the first two generations of Symmmetry products, released between 1987 and 1990.

== Symmetry 80836-based platforms ==

== Symmetry 2000 platforms ==

= Reference =

= External links =