Blue Gene Technology

A Blue Gene/P supercomputer at Argonne National Laboratory

          In November 2001 IBM announced a partnership with Lawrence Livermore National Laboratory to build the Blue Gene/L (BG/L) supercomputer, a 65,536-node machine designed around embedded PowerPC processors. Through the use of system-on-a-chip integration coupled with a highly scalable cellular architecture, Blue Gene/L will deliver 180 or 360 Teraflops of peak computing power, depending on the utilization mode.

The block scheme of the
Blue Gene/LASIC including
dual PowerPC 440 cores.

          Blue Gene/L represents a new level of scalability for parallel systems. Whereas existing large scale systems range in size from hundreds to a few of compute nodes, Blue Gene/L makes a jump of almost two orders of magnitude. Several techniques have been proposed for building such a powerful machine. Some of the designs call for extremely powerful (100 GFLOPS) processors based on superconducting technology. The class of designs that we focus on use current and foreseeable CMOS technology. It is reasonably clear that such machines, in the near future at least, will require a departure from the architectures of the current parallel supercomputers, which use few thousand commodity microprocessors. With the current technology, it would take around a million microprocessors to achieve a petaFLOPS performance.

          Clearly, power requirements and cost considerations alone preclude this option. The class of machines of interest to us use a “processorsin- memory” design: the basic building block is a single chip that includes multiple processors as well as memory and interconnection routing logic. On such machines, the ratio of memory-to-processors will be substantially lower than the prevalent one. As the technology is assumed to be the current generation one, the number of processors will still have to be close to a million, but the number of chips will be much lower. Using such a design, petaFLOPS performance will be reached within the next 2-3 years, especially since IBM hasannounced the Blue Gene project aimed at building such a machine.

One Blue Gene/L node board

          The system software for Blue Gene/L is a combination of standard and custom solutions. The software architecture for the machine is divided into three functional Entities arranged hierarchically: a computational core, a control infrastructure and a service infrastructure. The I/O nodes (part of the control infrastructure) execute a version of the Linux kernel and are the primary off-load engine for most system services. No user code directly executes on the I/O nodes.