The Superiority of Designer Genes

The Superiority of Designer Genes

By Tom R. Halfhill

TOM_HALFHILL.jpgWhile AMD and Intel boast about their upcoming dual-core processors, how would you like a computer with 131,072 processors? For a few million dollars, it’s yours.

IBM has dazzled the not-easily-impressed scientific community by breaking the world speed record with its new BlueGene/L supercomputer. BlueGene/L scored a whopping 70.72 trillion floating-point operations per second (teraflops) on the Linpack benchmark, which blew away NASA's brand-new Columbia supercomputer (51.87 teraflops) and doubled the performance of the previous world champion, NEC's Earth Simulator.

And BlueGene/L isn't even finished. It's a working prototype of a machine IBM will deliver to Lawrence Livermore National Laboratory next year. The prototype has only one-fourth as many processors as envisioned for the finished system. You would expect a world-class supercomputer like BlueGene/L to scream at a multigigahertz clock speed. But you would be wrong. BlueGene/L plods along at 700MHz. It's a great example of how multiprocessing can deliver superior performance without resorting to stratospheric clock frequencies.

Yep, there's good reason why AMD and Intel are betting that their new multi-core designs will boost PC performance. Besides its slow-poke clock speed, BlueGene/L has other oddities. It's based on a 5-year-old 32-bit PowerPC 440 processor core previously found only in chips for boring embedded applications, like networking equipment. It's a sound design, but not as advanced as the latest Pentium 4 or Athlon 64. It doesn't even have a floating-point unit (FPU), a requirement for scientific computing.

IBM had to graft a newly designed FPU onto the PowerPC 440 to make it suitable for a supercomputer. At the same time, IBM integrated two PowerPC 440 cores on one chip, just as AMD and Intel are doing with their dual-core chips. But whereas AMD and Intel will manufacture their dual-core wonders with the latest 90-nanometer fabrication technology, IBM is making BlueGene/L chips with an old-hat 0.13-micron process. Hey, it's good enough for 700MHz. The secret to BlueGene/L's success is massive parallelism. The finished supercomputer will have 65,536 dual-core chips with 131,072 processor cores. They're linked by five independent wiring networks for control signals and data.

Remarkably, one network runs at 1.4GHz, making BlueGene/L the first processor I've seen that drives an I/O interface faster than the CPU core. Usually, I/O runs slower than the core. BlueGene/L's massively parallel system architecture isn't easily imitated by PCs. Very little PC software has the parallelism inherent in many scientific applications. Nevertheless, IBM's multicore, multiprocessor, multinetwork supercomputer contains important clues about the future of general-purpose computing.

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