Thursday, September 21, 2000

One problem that we haven't yet satisfactorily addressed is the increase in temperature associated with increasingly tiny, and complex ICs. High operating temperatures can have many unwanted affects on a computer chip, and the device it is installed in. One of the more obvious affects is blazing hot laptop computers, where space is limited, and complex cooling systems cannot be employed. For safety, and engineering reasons then, hot processors don't make it into portable applications.

Heat stands as both a symptom, and, by its own effects, a cause of an underlying problem. That problem is electrical resistance. Save possibly for a few ultra-low temperature superconductors, all conducting materials - including those used to make the wires (or interconnects) in IC's - have a certain level of resistance to electricity; even if that resistance is extremely low. With literally hundreds of meters of tiny wires being crammed into such a small space, an IC can quickly become a miniature space heater. As this heat builds up, it poses the obvious threat of causing physical damage to the chip itself. Moreover, the excess energy interferes with the internal processes of the IC by jostling about the many electrons, and atoms, creating traffic jams, and generally lowering the efficiency of things.

A long standing approach to this problem is to employ heat sinks, and fans to drawn heat away from the IC in question. This has worked fairly well so far. At current performance levels, heat sinks made from aluminum, or sometimes copper, and cooled by air current have served well in large, high performance i386 systems. Larger systems, though, or those that have been pushed past their recommended performance levels, often employ more complex water cooling systems as a means of preventing overheating. As Moore's Law drives manufacturers to produce faster, and faster systems, however, some researchers envision a time around 2010, when liquid nitrogen will be required to cool systems running at 20-40Ghz. Under any circumstances, and most scientists and public safety officials would probably agree, expecting home-computer users to handle liquid nitrogen is a disaster waiting to happen. Clearly, in the long run, measures have to be taken to reduce heat production on a more fundamental level.

To tackle these problems, a number of solutions come to mind. The most obvious of these, is to simply increase the efficiency of the wires themselves by employing better conductors. This has long proven to be easier-said-than-done. For decades, developers have been stuck with using aluminum as their method of shuttling electrons about. Copper, an obvious step up from that mediocre-conductor, has for years proven to be a difficult material to work with, as it tended to poison the silicate material around it. Recently, though, IBM researchers made a breakthrough in this regard, and began to crank out copper-wire chips by the wafer-full. In the long run, this will prove very beneficial for chip manufacturers, as their ICs will require less electrical current to overcome the natural resistance of their wires, and thus generate less heat.

Another obvious solution is to reduce the amount of current used by improving the energy efficiency of the components themselves. This has happened to a large extent already. As transistors, capacitors, and wires have shrunk, they have also required less electricity to operate. Unfortunately, such has been the pace of progress that the number of new components being added to chips is sometimes largely offsetting - or at times outpacing - the benefits from miniaturization. The only other way to sufficiently reduce electrical requirements then, is to fundamentally alter the composition of the components themselves. Much of this has been, or will be done, with the adoption of copper-wiring processes, and with the development of Silicon-On-Insulator technologies, among others. One component, though, that has so far been left out, is one of the most important of all: the capacitor.

part 5: How To Express Your Magnetic Personality