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Evans and Sutherland E&S-1

Manufacturer Evans and Sutherland
Identification,ID E&S-1
Date of first manufacture1989
Number produced 6
Estimated price or cost-
location in museum -

Contents of this page:




Special features

Historical Notes


The Computer Division

In 1985, a European group lead by Jean-Yves Leclerc, with plans for developing a very high performance computer server, approached E&S for advice on getting started in the industry. After months of discussion, E&S brought the new group in as company employees. The announcement was made in 1986 in conjunction with the divisionalization and the group became known as the company's third division, the Computer Division. Because of its proximity to design tool suppliers, chip manufacturers, and a large high-tech labor force, Mountain View, California was chosen as the site for the Computer Division.

As research and development progressed, it was decided that the new division should target the supercomputer market instead of following its original charter to produce a computer server.

from tech reports

The Computer Division of Evans and Sutherland had announced the first two shipments of their first machine in October 1989. In November 1989 the parent company announced that the Computer Division is up for sale. Since no buyer was found the division has been closed by the end of the 1989. There are probably about six ES-1 machines, which have been produced, and which may find some use, but in all likelihood the inclusion of the ES-1 machine in this study appears to be only of historical interest.

This Specimen

Interesting Web Sites

Other information
from (Un-Official)
Evans & Sutherland Computer Division (ESCD)

Jean-Yves Leclerc was unable to find funding for a supercomputer project in Europe, so he came to the US to raise funding and interest. Dave Evans of Evans & Sutherland had been Leclerc's mentor during his graduate studies in the US, and Leclerc succeeded in persuading Evans & Sutherland to create a new division to build high-performance computers. The business logic was that many E&S customers were using Cray machines in conjunction with E&S graphic, and that a machine specifically tailored to the needs of visual simulation and seamlessly integrated with E&S graphics capabilities would find a ready market.

The machine was code-named "Orca", and was to be sold as the ES-1.

The project kicked off in 1986, and folded in January 1990.


The ES-1 had a two-level crossbar interconnect. At the first level, up to 16 processors were connected to up to eight memory cards. Second-level interconnect would have allowed up to 128 processors in a system, all sharing memory, albeit with some pretty daunting memory delays.

Each processor was in fact called a "functional unit" or "compute unit", and a card-cage populated with 16 of these CUs was referred to as a "processor" in ESCD terminology. This allowed favorable per-"processor" performance comparisons with other supercomputers!

The integer/control portion of the CPU had an instruction set that emphasized latency tolerance. Up to 8 integer load/store memory operations could be in flight at the same time, with precise exceptions guaranteed in the event of a fault. Branches had a variable delay slot, the end of which was signaled by a "split" bit in a subsequent instruction, which indicated that the tagged instruction marked a split in the instruction stream, and is the last to issue before the preceding branch condition is resolved.

The FPU was in fact an off-the-shelf design from Weitek.

The memory architecture was a bit unusual and complex. For example, the memory modules also contained much of the interrupt arbitration logic. The reasoning was that, since I/O channels and CPUs entered along the same axis of the crossbar, interrupt packets had to pass through memory to get to a CPU. Therefore, the CPUs were obliged to communicate their interrupt mask levels to the memory controllers, to allow interrupts to be sent to ready CPUs.


The non-commodity components were CMOS designs synthesised using the Silicon Compilers tools. Memory was MOS DRAM.


The OS was based on early versions of MACH from CMU. It was certainly the first multiprocessor version of Mach delivered to a customer (in Beta form, at least). The compilers used Compass front ends, but the back end was developed internally.

Strong Points

The physical packaging scheme was clean and economical. The ES-1 would have been the most powerful air-cooled machine of its day.

The compilers were very good at filling more load delay slots than the literature suggested should have been possible.

Weak Points

The architectural principles were too heavily compromised by the implementation technology and techniques. What started as a multithreaded machine ended up as merely a set of CPUs that supported a largish number (for the day) of outstanding memory requests.

The silicon compilation technology employed resulted in large, slow chips, limiting the chip yield to dangerously low levels and yielding a maximum clock speed of 40Mhz for the FPUs, and half that for the custom integer pipelines. This was not terribly impressive for a "supercomputer", even in 1989.

Because of a naive belief that the design was correct "because we simulated it", little or no provision was made to observe the internal state of the machine during bring-up.

The Fatal Flaw

The crossbar arbitration algorithm was patented. And defective. Rather than implement FIFO or round-robin, it used a scheme which alternated priority between the "rightmost" requestor and the "leftmost" requestor. Under load, requestors in the middle would get no service for unbounded periods of time. Memory delays of thousands of cycles were often seen. The project was in deep trouble by late 1989, but the need to redesign and respin the crossbar was the last straw. The project was shut down instead.

Lessons Learned

Don't believe what the design automation salesman tells you his tools will let you do.

There are never enough cycles to fully simulate a complex design before tape-out. Assume that there will be bugs, and that they will have to be hunted down.

If you have comments or suggestions, Send e-mail to Ed Thelen

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Updated April 30, 2000