In fact 6 of the current Top 10 are new to this list, and one other has had a significant upgrade since debuting at number 17 in the most recent list.
That upgraded machine is Sequoia which moved into the Number 1 spot with a sustained speed of 16.32 petaflop/s.
Sequoia, Based at the Lawrence Livermore National Laboratory, contains 1,572,864 CPU cores (the first to have more than 1,000,000) - a considerable increase over the 65,536 which took it to 17th place in the previous list. Oddly enough the speed increase almost exactly matches the 24-fold increase in the processor count. Also, although iTWire announced the development of this computer, and it's exact details nearly two years ago, the machine was un-named in the previous list.
There are plenty of other facts to glean from the list - for instance Peter Jackson's five identical Hewlett Packard machines have fallen off the bottom of the list and there are currently 6 Australian machines listed. Also, in the previous list, just the first 10 machines exceeded 1pf/s; this time there are 20 exceeding that level of performance. At the other end of the list, the lowest ranked November 2011 computer still in the list, South Africa's Tsessebe, moved from position 329 to 497. There are 167 computers new to the current list.
As always, Linux rules the roost - just 25 are running something else (mostly some other Unix). Only two are running Windows HPC.
Offering power efficiency of over 2,000 Mflops/watt, ALL of the IBM BlueGene/Q computers (20 in the current list) offer nearly double the efficiency of any other machine (the best being 1,266 Mflops/Watt achieved by the nameless Bull B505 machine in Barcelona). Interestingly, some of the least efficient machines are the Crays - Jaguar for instance, the first machine to break the 1Pflop/s barrier has only 1 sixth the efficiency at 377.5 Mflops/watt. This means it needs considerably more cooling to dissipate the heat produced by the processors.
Recent reports indicate that a new machine to be built on Canberra will be the fastest in the southern hemisphere, with a planned speed of 1.2 pflop/s. Prior to today's list, this would have taken 5th place on the list, but now it would only make 14th. Even worse, the machine won't be commissioned until early next year, meaning it won't be included until the June 2013 list, where it would be in doubt to make the top 25. In addition, plans are afoot for a 1.5 pflop/s machine in Perth to handle the computational requirements of the SKA radio telescope project.