Elxsi

Elxsi (now Tata Elxsi) was a minicomputer manufacturing company established in the late 1970s along with a host of other competitors (Trilogy Systems, Sequent, Convex Computer). The Elxsi processor was an Emitter Coupled Logic (ECL) design that featured a 50 nanosecond clock, a 25 nanosecond backpanel bus, IEEE floating point arithmetic and a 64-bit architecture. It allowed multiple processors to communicate over a common bus called the Gigabus. The operating system was a message based operating system called EMBOS. The Elxsi CPU was a microcoded design, allowing custom instructions to be coded into microcode.

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History

Elxsi was founded in 1979 by Joe Rizzi who had been a manager at Intersil. Much of the architecture of the Elxsi machine was designed by former Stanford University professors Len Shar and Balasubrimanian Kumar. Another key contributor to the design was Harold (Mac) McFarland, who was also a key designer on the team that created the PDP-11. George Taylor (on the IEEE standard committee and a student of Cal Berkeley Professor William Kahan) provided a key design for the IEEE floating point unit. Elxsi was bought out by Gene Amdahl with money that was left over from the Trilogy venture.

Venture investors in Elxsi included Tata Group (India) and Arthur Rock. In the early 1990s, however, Elxsi went out of business because of the general shift away from the use of mainframes in the global computer industry and the advent of the personal computer. The Tata Group kept the name Tata Elxsi but it now belongs to the Tata group of companies.

The large range of hardware expansion gave the machine some success in departmental technical computing environments. The 64-bit registers and ability to do parallel adds within them gave it an unanticipated advantage in COBOL benchmarks, where it outperformed some mainframes. And the extreme independence of the CPUs (lack of cache snooping and invalidation), coupled with the ability to lock processes into register sets and later, the ability to partition the caches, gave it some success in real time applications.

Hardware

The Elxsi machine was a mini-supercomputer: a category of computers that was larger than a VAX 11/780 and smaller than a mainframe. This market segment disappeared as high end microprocessor based systems became more powerful.

The architecture was unusual, especially for its day. The system bus connected as many as 12 CPUs and I/O processors. Each CPU was built from 3 large boards of ECL gate arrays. Key elements of its instruction set architecture were:

Software

The EMBOS OS was written entirely from scratch in a slightly extended Pascal. It was a multi-server architecture (like GNU Hurd, but long predating that project). The UI was Unix-like, especially at the shell level, with similar concepts but different commands, syntax, etc. (e.g. "files" instead of "ls"; "find" instead of "grep"). Later, a Unix kernel was hosted on top of the lower-level servers so that EMBOS and Unix processes and users could co-exist (ENIX). VMS compatibility software running on top of EMBOS was also added to ease porting of VAX applications.

Famous employees

Although Elxsi was not a financial success, many of its employees did go on to fame and fortune.

References

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