A Brief History of Supercomputers

Processor Trajectory

Both the Intel 486 and Pentium PC processors had about the same performance as Sun-3 and SPARCstation-1 workstations that were proving to be so popular. Comparatively, the supercomputers were still definitely much faster than those in a PC, but supercomputer manufacturers knew that making their own processors was becoming a burden, forcing their prices to stay high.

On the other hand, Intel was improving their processors quickly with faster versions almost every year, and they fit into the same socket, saving customers money. In the span of five years, they came out with three new processors with increasing speeds and sophistication – all of them affordable by millions of people.

In the early part of the 1990s the pace of PC CPU development was quick, and the quantities of PC processors sold were much larger than supercomputer processors and growing rapidly. However, they were still behind in terms of performance. Despite Cray systems moving from custom processors to workstation processors, they did not have nearly the volume of sales of PC processors.

The latter half of the 1990s was a very hectic time for PC CPUs. Intel launched the Pentium Pro in November 1995, with 5.5 million transistors, a big jump from the 3.3 million transistors in the Pentium. The clock speed started at 150MHz, but subsequent versions rose to 166 and 200MHz The FSB speeds ranged from 60 to 66MHz. The Pentium Pro had a large on-package L2 cache for a PC CPU, with the first versions starting at 256KB, then increasing to 512KB and ultimately 1MB.

The Pentium Pro was a superscalar processor and supported MMX, as well, which added more performance to the CPU. It also had out-of-order execution to make it more efficient. The Pentium Pro had a 36-bit address bus that was usable by physical address extension (PAE), allowing access to 64GB of memory. The Pentium Pro could be used in dual- and even quad-socket configurations, creating SMP solutions. The socket was the same for all sockets on the board.

Perhaps one of the most important points about the Pentium Pro is that it was the first PC CPU to be used in a supercomputer, ASCI Red. ASCI Red was the fastest supercomputer until late 2000 and was the first supercomputer to reach 1TFLOPS, achieving 1.06TFLOPS in December 1996.

PC processors continued to improve throughout the 1990s, with rapid escalation of processing power and the emergence of AMD as a competitor to Intel. At the close of the decade, the pace of innovation and release of new PC processors was staggering. A processor was released almost every year or 18 months, and sometimes two processors were released in a year. PC processors were steadily increasing in clock speed and L2 cache size. CPUs became superscalar and added SIMD instructions, providing more performance for applications that could use it. However, despite all these developments, PC processors were still 32-bit.

Supercomputer Processors in the Latter 1990s

Recall that Cray launched the T3E in 1996. In February 1996, Cray was acquired by SGI. While SGI owned Cray, only one new Cray model line was released, the Cray SV1 in 1998. It went back to the Cray vector systems using processors made by Cray and was backward compatible with J90 and Y-MP software. Unlike previous processors, though, those in the SV1 included a vector cache, a departure from earlier designs. It ran at 300MHz, but later variants ran at 500MHz. The SV1 node design was something like an SMP system in the fashion of the J90. These nodes could be connected to create a clustered SMP vector system.

NEC launched its SX-5 system in 1998. It could reach 4TFLOPS of performance. Each node of the system used 16 CPUs with up to 128GB of main memory. It could connect up to 32 nodes for a total of 4,096GB of memory.

SGI announced a large-scale HPC system, the SGI Origin 2000, in 1996. It could accommodate from 2 to 128 MIPS CPUs. These were the MIPS R10000 processors that ran at 180MHz initially, but then increased to 300 and 400MHz. One advantage SGI had was that the processors weren't just used for supercomputers like the Origin 2000. They were also used for SGI workstations. The SGI O2 workstation was introduced in 1996 and used a single R10000 MIPS processor than ran from 150 to 400MHz.

The classic line of supercomputers – Cray, NEC, and now SGI – made good progress in the 1990s. In some cases, they used more commodity processors such as the DEC Alpha in Cray systems or even the MIPS in the SGI Origin.

Overall, supercomputer processors also had some good clock speed gains during this time. In terms of architecture, Cray and NEC had turned toward distributed parallel systems connected with a high-performance network. The SGI systems were SMP, and both Cray and NEC had parallel SMP systems.

Although these systems were dominant in HPC, they were still awfully expensive, running into the millions. As such, they were very centralized and shared across a wide range of users. Companies and research institutions could only afford one system that was centralized and tightly controlled. Moreover, because the systems were quite costly, only certain applications could run on them. If you will, they were still very much the model of a priesthood, where the lowly user had to ask permission to run an application.

The 1990s were critical to both “classic” supercomputers and PC systems. Both had advanced very quickly, setting a trajectory into the early 2000s.