Cray XK7

Cray XK7

Titan, an XK7 supercomputer at Oak Ridge National Laboratory
Operators	Cray Inc.
Architecture	AMD Opteron 6200 Interlagos series 16-core CPUs Nvidia Tesla K20 Kepler series GPUs
Power	45 to 54.1 kW per cabinet
Operating system	Cray Linux Environment
Memory	16 or 32 GB ECC DDR3 per CPU 5 or 6 GB ECC GDDR5 per GPU
Speed	Theoretical peak of 50 petaFLOPS
Ranking	TOP500
Web site	www.cray.com/Products/Computing/XK7.aspx

XK7 is a supercomputing platform, produced by Cray, launched on October 29, 2012. XK7 is the second platform from Cray to use a combination of central processing units ("CPUs") and graphical processing units ("GPUs") for computing; the hybrid architecture requires a different approach to programming to that of CPU-only supercomputers. Laboratories that host XK7 machines host workshops to train researchers in the new programming languages needed for XK7 machines. The platform is used in Titan, the world's second fastest supercomputer in the November 2013 list as ranked by the TOP500 organization. Other customers include the Swiss National Supercomputing Centre which has a 272 node machine and Blue Waters has a machine that has Cray XE6 and XK7 nodes that performs at approximately 1 petaFLOPS (10¹⁵floating-point operations per second).

XK7 is scalable up to 500 cabinets, each contains 24 blades and each blade contains 4 nodes (1 CPU and 1 GPU per node). The CPUs available are of the 16-core AMD Opteron 6200 Interlagos series and the GPUs are of the Nvidia Tesla K20 Kepler series. Each CPU can be paired with either 16 or 32 GB of error-correcting code memory (ECC) while the GPUs have either 5 or 6 GB of ECC memory depending on the model of GPU used. The nodes communicate with each other via the Gemini Interconnect; each Gemini chip services 2 nodes with a capacity of 160 GB/s. Depending on the components used, a full cabinet will consume between 45 and 54.1 kW of electricity which is converted into heat; thus the cabinets need cooling, either by air or water.

XK7 based machines run the Cray Linux Environment which incorporates SUSE Linux Enterprise Server. Code to run on an XK7 machine can be written in a range of programming languages. The hybrid architecture requires different programming to conventional CPU-only supercomputers; Oak Ridge National Laboratory and the Swiss National Supercomputing Centre hold workshops to educate researchers on the new programming approach.