ETA10

The ETA10 was a line of supercomputers manufactured by ETA Systems (a spin-off division of CDC) in the 1980s and which implemented the instruction set of the CDC Cyber 205.

Historical development

Control Data Corporation (CDC) had a strong history of creating powerful mainframe computers, with an emphasis on the scientific computing customer base. One of the most famous computer architects to emerge from CDC was Seymour Cray. While he went on to form his own company, work continued at CDC in developing high-end mainframe computers (aka supercomputer) — led by another famous architect, Neil Lincoln. As Cray competed against CDC, it became apparent to top management that it needed to decrease the development time for the next generation computer — thus a new approach was considered for the follow-on to the CDC Cyber 205.

After being spun off from CDC in September, 1983, ETA had the goal of producing a supercomputer with a cycle time under 10ns. To accomplish this goal, several innovations were made by ETA. Among these are the use of liquid nitrogen for cooling the CMOS circuits of the computer.

The ETA10 successfully met the company's initial goals (10 GFLOPS), with some models achieving a cycle time of about 7ns, which was considered rapid by the standard of the mid-1980s. The planned 1987 follow-on was supposed to be designated CYBER-250 or ETA-30, as in 30 GFLOPS. ETA was eventually reincorporated back into CDC, and ETA ceased operations April 17, 1989.

Operating systems and applications

The ETA10 series could run either ETA's EOS operating system, which was widely criticized for various problems, or a port by Lachman Associates, a software personnel firm, of UNIX System V (Release 3). While EOS suffered a reputation for poor quality, ETA's UNIX was better received by customers.

Use of the ETA10 was rather complicated, and required all programs be loaded via attached Apollo Computer workstations. The program would then run once, and to run again would require re-loading from the Apollo. The ETA10 itself had no graphical console or local network interface, and all visualization of resulting data was performed by separate workstations after being retrieved from the Apollos. Programming for the ETA10 series could be done in FORTRAN, C, or CDC Cyber 205 assembly language.

Criticism

Despite eventual adoption of UNIX, poorly developed system software remained one flaw of the ETA10 line. According to one description of the system:

Without NSF funding, the von Neumann center could be doomed. "I don’t think we can function without federal support," says Cohen. Even if the center does operate at a vastly reduced level, its machines continue to be plagued by software problems. The NSF review panel found that the ETA10 suffered a software failure once every 30 hours, and that its ability to run programs on more than one of its eight processors at any one time was poor. Although its hardware is still considered state-of-the-art, the overall package is an "extremely immature computer system," the panel concluded.

Anderson, Christopher (Nov. 27, 1989). NSF Supercomputer Program Looks Beyond Princeton Recall. The Scientist 3 (23), p. 2. (

It is a mistake to believe that ETA's demise was based solely on operating system choice or existence. The Fortran compiler (ftn200) had not changed from the CDC205. This compiler retained vendor-specific programming performance features (known as the Q8* subroutine calls) in an era when supercomputer users were realizing the necessity of source code portability between architectures. Additionally, the compiler optimizations were not keeping up existing technology as shown by the Japanese supercomputer vendors as well as the newer minisupercomputer makers and competition at Cray Research.

In general, computer hardware manufacturers prior and up to that period tended to be weak on software. Libraries and available commercial and non-commercial (soon to be called open-source) applications help an installed base of machine. CDC was relatively weak in this area - it is worth noting that some of the best operating systems that CDC provided to customers was a productized version of an OS written by Lawrence Livermore Laboratories.

Models

The ETA10F and ETA10-G (7 ns clock cycle) were the highest-performing members of the ETA10 line, and used liquid nitrogen cooling to achieve rapid cycle times.

Less-costly air-cooled versions were later offered, such as the two-processor ETA10-Q (19 ns clock cycle), and the ETA10-P, which was also called "Piper".

Any of the ETA10 models could be built in either single- or multi-processor configurations.

Performance

Between the highest-performing, liquid-nitrogen cooled models (ETA10-E, G, etc.) and the cheaper, air-cooled models (ETA10-P, Q, etc.), the ETA10 line spanned a 27:1 performance range. Peak performance on the top-of-the-line models reached 10 GFLOPS.

According to LINPACK benchmarks, an ETA10 with a single processor achieved 52 MFLOPS on 100^2 LINPACK.

Technology and computer architecture

The ETA10 line adopted novel approaches to physical construction, as well as innovative computer organization and lay-out processes:

CMOS circuits

The ETA10's CPU was built on a single board, using 44 layer PCB. The ETA-0 line is also notable for using CMOS logic technology, which has become the standard process used to manufacture the great majority of microprocessors in the 2000s.

The benefit of using CMOS lies partly in its rapid switching speeds, in the low tens of picoseconds; the ETA10 line put this to use with an approximately 100 MHz clock speed. Further, although slower than ECL at the time, CMOS circuitry could be laid out on a wafer more densely than permitted by ECL, thus ameliorating various off-chip and on-chip delays. These delays were managed through careful tuning of each PCB manufactured in conjunction with the logic technology - incorporating two key technologies that became known as JTAG and BIST. The IC's used for the ETA product were 20K Gate Arrays fabricated using 1.25 micrometre technology that were accessible from the VHSIC program at Honeywell - mainstream commercial technology was at the 3 to 5 micrometre technology at that timeframe.

The IC's were designed using a combination of internally developed tools (simulators and placement), while using some of the first commercial EDA tools from a vendor called Mentor Graphics for schematic capture. Prior to the use of schematic capture at ETA, the designers had used textual netlists to describe the interconnection of the logic circuits.

Noteworthy is that ETA had to invent methods for creation of 44 layer PCB's, as there were no external vendors supplying such advanced technology at that time.

Liquid nitrogen cooling

The highest performance was achieved by cooling the CMOS logic with liquid nitrogen. Although such cooling could potentially speed up execution by a factor of four, in practice the liquid nitrogen cooling yielded an approximately twofold execution speed increase over air-cooled systems. However, because liquid nitrogen cooling yielded only marginal performance benefits, none of the ETA10 systems used such cooling for either the local or system-wide memory subsystems.

It is of particular note that in order for this type of cooling to be effective, a closed loop system was required. ETA had to innovate to make this possible, since there were not any commercially available solutions in the market.

Fiber-optic interlinks between subsystems

The ETA10 used fiber-optic lines for communication between processors and I/O devices, a novel approach for systems interconnection in the 1980s.

Installations

Before ETA Systems was reincorporated into CDC, a total of 25 systems were delivered. Among the recipients were:

Florida State University (took delivery of the first ETA10 system, serial number 1, on January 5, 1987)
Johnson Space Center
John von Neumann Supercomputer Center (when no buyers could be found for the two ETA10 machines at this center, they were destroyed with sledgehammers to prevent illicit use)
Purdue University (contributed to ETA System V, the System V UNIX variant that ran on the ETA10).
Tokyo Institute of Technology Took delivery of an 8 CPU liquid cooled system in 1988
Academia Sinica
Deutscher Wetterdienst