A consequence of doing useful work with computers is the production of heat. Every watt of energy that goes into a computer is converted to a watt of heat that needs to be removed, or else the computer will melt, burst into ames, or meet some other undesirable end. Most computer systems in data centers are cooled with air conditioning, while some high-performance systems use contained liquid cooling systems where cooling uid is typically piped into a cold plate or some other heat exchanger. Immersion cooling works by directly immersing IT equipment into a bath of cooling uid. The National Security Agency’s Laboratory for Physical Sciences (LPS) acquired and installed an oil-immersion cooling system in 2012 and has evaluated its pros and cons. Cooling computer equipment by using oil immersion can substantially reduce cooling costs; in fact, this method has the potential to cut in half the construction costs of future data centers.

Modern supercomputer performance is principally limited by power. TSUBAME-KFC is a state-ofthe-art prototype for next-generation TSUBAME3.0 supercomputer and towards future exascale. In collaboration with Green Revolution Cooling (GRC) and others, TSUBAME-KFC submerges compute nodes configured with extremely high processor/component density, into non-toxic, low viscosity coolant with high 260 Celsius flash point, and cooled using ambient / evaporative cooling tower. This minimizes cooling power while all semiconductor components kept at low temperature to lower leakage current. Numerous off-line in addition to on-line power and temperature sensors are facilitated throughout and constantly monitored to immediately observe the effect of voltage/frequency control. As a result,TSUBAME-KFC achieved world No. 1 on the Green500 in Nov. 2013 and Jun. 2014, by over 20% c.f. the nearest competitors.