Summer is due to end. Hot days are diminishing. Well, are they? The temperatures outside are likely to drop, but looking at datacenters, temperatures are going up. Not surprisingly because the number of power hungry processors are increasing. Every Watt a processor needs, is ultimately transformed into heat. The problem is, that if a processor needs an aditional 1 Watt, the power supply needs more than that 1 Watt due to losses. The losses itself are ultimately transformed in heat as well. So to cool all of the servers the airco needs to be upgraded as well, drawing even more power from the grid.
IBM has, as many other companies in the world, looked for a way to minimize the amount of power a processor needs. One way to do so was to exchange the aluminium interconnects in a processor with copper. Copper has a much, much better conductivity than aluminium. Every Ohm of resistance you don't have to overcome will save you power (equals heat) in the end. To give you an idea. In the latest processor of IBM 267 million transistors are residing. All with three leads which have to be connected. Must end up with miles of internal wiring.
Problem with copper: it doesn't 'stick' on silicium. Ai, that's too bad. So, the hard-core researchers of IBM (and all other chip-minded companies in the world) started to find ways to solve this sticky problem. After more than 25 years, IBM found a way to let copper 'stick' to silicium. That was in the late '90's. I can tell you: some bottle popped open that day!
Since then other techniques like Silicon-on-Insulator, Stretched Silicium, and Low-k dielectric made it possible to even lower the dissipated power of chips. Also chips with a Silicium-Germanium combination (SiGe) was a very good way to process very high frequencies without too many losses. Every cell-phone in the world uses this technique.
Recently, IBM made another breakthrough. We developed, in cooperation of Georgia Institute of Technology, a SiGe chip which can operate at 500 GHz (that's half a Tera Hertz!). Wow! Yet, one problem to solve. This frequency is (for the time being) only possible when cooled to a chilly minus 268 centigrade. Like I said: hot days are diminishing...