10GHz Processors And Moore's Law

AntiFreeze writes "There is an interesting story on MSNBC about Intel's attempts at producing chips capable of running at faster than 10 gigahertz. There was a previous /. article in early December about this here. This article from MSNBC is much more detailed (both technically and non) than the original article referenced from December, and provides a very intriguing look at what Intel's planning to do over the next four years, and what they'll have to show the general public as soon as April 1st. And as always, there's the heated /. argument about Moore's law buried in there, too."

Comments

Errm.....

[Ricky Cousins]

They'll have something to show on April 1st? Am I the only one who raised an eyebrow at this bit?

line widths

[Veteran]

Several interesting effects occur as line widths decrease. The first is that the working voltage has to go down: at .1 micrometer a one volt difference between the two sides of the line gives and electric field of 10 million volts per meter - which begins to approach the insulation capability of the best known insulator. In other words the insulators start to arc through. The cell wall of a neuron is so thin that the neuron is restricted to voltages of about 90 millivolts by this effect. The electric field problem is why present day processors operate at the approximately the 2 volt level.

Lowering the voltage has some good effects - the main one is that the power consumption drops as the square of the voltage (assuming Ohms law). However lowering the voltage causes everything to run slower. The old fashioned 4000 series CMOS chips were much faster at 15 volts than they were at 5 volts.

Chips get faster when they shrink because the capacitances decrease as the surface area of a conductor shrinks; cut the feature size by a factor of two in both directions and the capacitance is down by a factor of four. However there is another effect which occurs as everything shrinks; the insulation between features shrinks, and that shrinking feature increases the parasitic capacitance between the two features.

In the past the increase in capacitance caused by the thinning of insulators has not been a significant effect in limiting clock speeds but there comes a point where the effect does become important. In neurons the cell walls are so thin that the capacitance effects of the thin dielectric limit signal propagation speeds in the neuron to about 180 miles per hour or so. Long axons have thick sheaths to cut the capacitance and increase the signal propagation speeds.

This increasing capacitance with the decreasing dielectric thickness combined with the decreasing speed from the lowered voltages will eventually put an effective cap on the clock speed of silicon devices. The only big trick left in the book is too switch to Diamond based semi conductors - which are as much better than silicon than silicon was than germanium - and that will give us some more speed. Above a certain frequency Nature itself changes the way it does things. At RF frequencies bulk devices like crystals function - at the frequencies of light waves only atomic devices can switch from one state to another quickly enough.

In other words at some point in the near future we are going to reach a point where simple die shrinking won't be enough to crank up clock speeds any more. Enjoy things while they last - but another factor of a thousand increase in clock speed (Apple II one megahertz to present day one gigahertz) is going to be very difficult to achieve.