After another 14 ICE 8400 racks containing Westmere processors were added in 2011, Pleiades ranked seventh on the TOP500 list in June of that year at a LINPACK rating of 1.09 petaflops, or 1.09 quadrillion floating point operations per second. InfiniBand DDR and QDR fiber cables are used to connect the all of nodes to each other, as well as to the mass storage systems at NAS and the hyperwall visualization system, creating a network made up of more than 65 miles of InfiniBand fabric, the largest of its kind in the world. Pleiades is built in a partial 11-D hypercube topology, where each node has eleven connections to eleven other nodes, with some making up to twelve connections to form a 12-D hypercube. In 2012, NASA and partners SGI and Intel began working on the integration of 24 new Altix ICE X racks with Intel Xeon eight-core E5-2760 Sandy Bridge processors to replace 27 of the original Alitx 8200 racks containing quad-core Harpertown processors. With a total of 126,720 processor cores and over 233 terabytes of RAM across 182 racks, the expansion increased Pleiades' available computing capacity 40 percent. Each new Sandy Bridge node has four networking links using fourteen data rate (FDR) InfiniBand cable for a total transfer bandwidth of 56 gigabits (about 7 gigabytes) per second. In early 2013, work began on a larger hardware refresh for Pleiades, ultimately removing all of the original 4-core Harpertown processors and adding 46 SGI ICE X racks with 10-core Intel Xeon E5-2680V2 (Ivy Bridge) processors. When installation was complete in August 2013, the system's overall peak performance increased 62% from 1.78 petaflops to 2.87 petaflops. The system was slowly upgraded again between January and April 2014, adding another 29 racks of Ivy Bridge nodes and increasing the system's theoretical computational capability to 3.59 petaflops. To make room for the expansion, all of the system's remaining Nehalem nodes and 12 Westmere nodes were removed. In late 2014, more Westmere nodes were removed to make room for new Intel Xeon Haswell processors, increasing the theoretical processing power by one petaflop to 4.49 petaflops. In January 2015, additional Haswell nodes were installed and released to users, giving Pleiades a new peak theoretical processing capacity of 5.35 petaflops.