Heavyweights of the supercomputing world

The names of boxing's heavyweights are never forgotten – and it's the same with the champs of the supercomputing world.

These machines truly are like no others. Each is computationally more muscular than its predecessor; and for a while, each has claimed the title of the fastest computer in the world.

But, as the calamitous fall of 'Iron' Mike Tyson showed us, champions are built to be felled. And so we've seen supercomputers come and go, growing from single processor machines capable of a few thousand operations per second to systems like IBM's Roadrunner and the Cray XT Jaguar, the latter boasting a massive array of 45,000 AMD Opteron processors.

But exactly why do we need all this power? How much electricity does it take to power a supercomputer? What types of technology will tomorrow's supercomputers use? And how did it all begin? Round one begins now.

The rise of fast machines

For some time, the history of the fledgling supercomputer was the history of computing itself.

At the dawn of the digital age, devices like the Colossus Mark 1 and 2, and ENIAC filled entire rooms. They existed simply to crunch numbers far beyond human abilities. The term 'supercomputer' didn't enter common parlance until the 1960s, and it's often associated with just one famous individual – Seymour Cray. Cray's name is virtually synonymous with the supercomputer.

He started designing machines while working for Control Data Corporation (CDC), a company that had produced the fastest computers in the world for nearly a decade. Cray set himself the goal of creating a computer 50 times faster than the quickest system being sold by CDC at the time, the 48-bit 1604. It took him years, causing some consternation among CDC's management, but in 1964 the CDC 6600 came on the market.

Until the 1960s, computer processing power was measured by how many thousands of operations per second (OPS) a computer could perform. Colossus sported 5,000 OPS, ENIAC 100,000 OPS, and the fastest machine of the 1950s – IBM's catchily named AN/FSQ-7 – still only offered 400,000 OPS. By the time the CDC 6600 arrived, IBM had tripled the speed of its fastest system – the infamous 7030 Stretch – thanks to its adoption of transistors. But the CDC 6600 upped the ante. While Stretch could manage 1.2 MFLOPS (1,200,000 FLOPS), the CDC 6600 was 2.5 times faster, giving 3 MFLOPS. Note also that machines had switched from integer OPS to floating point FLOPS at the turn of the decade.

The leap in processing power given by the CDC 6600 has defined the concept of the supercomputer. Five years later, CDC made an even bigger step forward. The 7600 provided more than 10 times the performance of the 6600, giving 36 MFLOPS, and the trend continued, with the STAR-100 tripling the score in another five years to 100 MFLOPS. Within two years, Seymour Cray had broken away from CDC to form his own company. Its first product, the Cray 1, hit 250 MFLOPS in 1976.

Since then, supercomputer performance has increased by orders of magnitude every decade. The first GFLOP supercomputers (a thousand MFLOPS) arrived in the early 1980s, and the TFLOP level (a thousand GFLOPS) was exceeded by Intel's ASCI Red in 1997.

In 2008, IBM's Roadrunner became the first PFLOP supercomputer, achieving another thousand-fold increase in speed. At the same time, the fastest desktop quad-core processors contained in personal computers are achieving over 50 GFLOPS – the same as supercomputers of the early 1990s.

What makes a computer super?

What made the first true supercomputers so much faster than the previous systems?

The answer really is quite simple: parallelism. The CDC 6600 was still what would be called a single-processor system, with just one central processor (CP). However, this was also assisted by a series of 10 slower peripheral processors (PPs), which ran in parallel.

The CP itself only handled mathematical and logic operations, while the PPs performed all of the memory and input/output tasks. Since the CP was handling a much smaller subset of operations, it could be run faster. The other important element was the switch from thermionic valves (vacuum tubes) to transistors, which offered faster switching speeds. These factors taken together meant that the CDC 6600's CPU could run at 10MHz while other supercomputers of the day were operating at around 1MHz.

Since memory at that time was around 10 times faster than most supercomputer CPUs, the CDC 6600's architecture ensured that operations took full advantage of the bandwidth. The CDC 6600's PPs were each allowed access to the CP for one tenth of the time. So, although these were running slower than the CP, they were able to keep data flowing. The CDC 6600's CP also contained 10 function units internally, which enabled it to work on instructions in parallel. This was the first implementation of a superscalar processor design.