Editing IBM Blue Gene (section)

===Design===
The design of Blue Gene/P is a technology evolution from Blue Gene/L. Each Blue Gene/P Compute chip contains four [[PowerPC 400#PowerPC 450|PowerPC 450]] processor cores, running at 850&nbsp;MHz. The cores are [[cache coherence|cache coherent]] and the chip can operate as a 4-way [[Symmetric multiprocessing|symmetric multiprocessor]] (SMP). The memory subsystem on the chip consists of small private L2 caches, a central shared 8&nbsp;MB L3 cache, and dual [[DDR2 SDRAM|DDR2]] memory controllers. The chip also integrates the logic for node-to-node communication, using the same network topologies as Blue Gene/L, but at more than twice the bandwidth. A compute card contains a Blue Gene/P chip with 2 or 4&nbsp;GB DRAM, comprising a "compute node". A single compute node has a peak performance of 13.6&nbsp;GFLOPS. 32 Compute cards are plugged into an air-cooled node board. A [[19-inch rack|rack]] contains 32 node boards (thus 1024 nodes, 4096 processor cores).<ref>{{ cite journal |title=Overview of the IBM Blue Gene/P project |journal=IBM Journal of Research and Development |date=Jan 2008 |doi=10.1147/rd.521.0199 |volume=52 |pages=199–220}}</ref>
By using many small, low-power, densely packaged chips, Blue Gene/P exceeded the [[Performance per watt|power efficiency]] of other supercomputers of its generation, and at 371&nbsp;[[FLOPS per watt|MFLOPS/W]] Blue Gene/P installations ranked at or near the top of the [[Green500]] lists in 2007–2008.<ref name=Green500/>