Four Paths To Acceleration

Computer engineers pushing the limits of accelerator chips are experimenting with four main technologies: FPGAs, ASICs, graphics processors, and video game chips. Each has pros and cons.

FPGAs present designers with a blank slate of silicon, which can be reprogrammed as needs arise. They're extremely hard to program but able to perform hundreds or thousands of operations at once, compared with general-purpose microprocessors, which execute instructions in series. Cray and SGI are the top suppliers of systems that use FPGAs, and Linux Networx plans to enter the market this year with a chip that will sit on the front-side bus rather than connecting through PCI-X, which the company says will yield faster computing speeds.

ASICs like ClearSpeed's CSX600 chips perform operations when they encounter data, rather than waiting to be issued instructions from software. ClearSpeed makes a dedicated ASIC for high-performance computing that can plug directly into standard x86 boards. The chips are easier to program than FPGAs but still don't support standard C and Fortran. IBM fabricates the semiconductors for ClearSpeed and recently started reselling its boards.

Graphics processors from Nvidia and ATI Technologies provide superhigh floating point performance--perhaps eight times more than a general-purpose processor--and they're relatively cheap. Drawbacks include only "single-precision" or 32-bit decimal accuracy, compared with the 64-bit double-precision technology users prefer. Users also need to program directly to the hardware, without an abstract programming environment.

Game technologies such as IBM's Cell Broadband Engine use more conventional software techniques, like library calls and compilers, than other accelerators and try to apply the physics of light and mechanics used in video games to other application domains. IBM designed the Cell chip in a partnership with Sony and Toshiba for Sony's upcoming PlayStation 3 console. IBM says it could play a role as an accelerator in servers for apps including scientific supercomputing. The chip consists of a conventional microprocessor surrounded by special floating point accelerators. But Sony has delayed the release of PlayStation 3. If Cell doesn't succeed in the consumer market, its days as a business technology could be numbered.

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In Depth: Supercomputers Get A Speed Boost From Specialized Chips

Illustration by Viktor Koen