From a different angle 
http://don.cc.vt.edu/
http://computing.vt.edu/research_computing...essrelease.html
http://www.mellanox.com/news/press/pr_090203.html
QUOTE
Where do you put 1,100 G5s? The answer is not anywhere you want. The facility is housed in 3,000 square feet of Virginia Tech's 9,000-square-foot data center. Varadarajan said that they also had to build a new cooling system to cool all of the G5s as the existing AC system would have to move air in the floor at speeds exceeding 60 miles per hour to meet the cooling demand. The new cooling system works like a distributed refrigerator that uses cooled liquid fed to smaller air driven air conditioning units housed all throughout the facility. Without the cooling system, Varadarajan said that the temperature in the facility would increase to over 100 degrees within two minutes and components would be damaged within several minutes. Virginia Tech also constructed a UPS and 1.5 Megawatt backup diesel generator for the facility.
The system costs $5.2 million for the G5s, racks, cables, and Infiniband cards. Virginia Tech spent and addition $2 million on facilities, $1 million for the air conditioning system and $1 million for the UPS and generator.
http://don.cc.vt.edu/g5sinracks/slides/IMG_2355.JPG