If you think about sheer performance-per-watt potential, it's pretty hard to beat a supercomputer. So any company with gargantuan transaction processing needs might want to scout the latest Green500 list for insight.
This list was brought to my attention by SGI, which has 11 entries in the top 100 greenest systems: all of SGI's entries are SGI Altix ICE models, those of the water-cooled door design that I wrote about a couple of months ago. SGI claims that the ICE supercomputers are, on average, 32.8 percent more energy-efficient than the typical system listed on the Green500 list. Altix ICE is designed to remove up to 95 percent of the heat created by the computer.
IBM actually is the maker of the top-ranked system on the Green500. In fact, it looks as if it's the maker of ALL of the top 10, which is a pretty big achievement.