High Frequencies in Computer CPUs

SGT

The current in a wire moves according to an electric field and the moving electrons generate a magnectic field, so in a wire, in the air or in vacuum we have allways a varying electromagnectic field.

Integral

I do not have a cell phone but I do have older technology 900Mhz portable phones. These are so common that I do not even consider an old fashioned hard wired phone. To communicate with the base station my phone broadcasts a weak 900MHz signal.

What ever speed your computer is operating at, mine is ~2GHz, that clock rate must be an actual signal produced by the motherboard. It is an electromagnetic signal carried mainly by the traces on the motherboard but it is impossible to constrain that frequency to the conductors alone. There will always be some power in electromagnetic radiation surrounding the conductors. This signal is essentially broadcast. It is a very weak signal but a signal none the less.

Pengwuino

Well I'm talking about the old old old phones that are actually hard wired into the wall :D

Integral

Even an old fashioned hard wired Telephone must produce some EM around the wires carrying the signal. It is not in the GHz or perhaps even in the RF range, but it is there. Keep in mind that ALL conducting wires are surrounded by a magnetic field. If the signal the wire is transporting is changing then so is the surrounding magnetic field. A changing magnetic field implies EM radiation. The frequency of the EM radiation will be determined by the frequency content of the signal on the wire. This is basic, inescapable physics.

pervect

Clock speed vs CPU speed has become quite a marketing game. See for instance

http://www.computeruser.com/articles...1,0801,03.html

From an Electromagnetic interference standpoint, the speed of the clock signal is probably not going to be as important as the speed that the bus operates at, as the clock would feed only one pin on the CPU, and the bus would feed long wires which radiate better.

It is quite true that a CPU has to be shielded to avoid interference with TV's. The fast rise-times of signals in CPU's allow them to radiate multiple harmonics of the fundamental frequency. Problems with interference are not unheard of in the real world - sometimes this is due to poor shielding on the CPU, sometimes it's due to the TV being sensitve to signals outside the broadcast band range.

For completeness, I ought to look up the TV broadcast bands, but I have to run to the store before they close.