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Intel Devises Chip Speed Breakthrough
Chad Wood writes "According to the New York Times (free reg. req.), Intel has demonstrated a research breakthrough, making silicon chips that can switch light like electricity. The article explains:''This opens up whole new areas for Intel,' said Mario Paniccia, a an Intel physicist, who started the previously secret Intel research program to explore the possibility of using standard semiconductor parts to build optical networks. 'We're trying to siliconize photonics.' The invention demonstrates for the first time, Intel researchers said, that ultrahigh-speed fiberoptic equipment can be produced at personal computer industry prices. As the costs of communicating between computers and chips falls, the barrier to building fundamentally new kinds of computers not limited by physical distance should become a reality, experts say.'"
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Disclaimer: I am a Ph.D. in fiber optic physics
This is a 2 Gb/s modulator, whereas III-V semiconductor modulators above 40 Gb/s are commericially available.
A modulator by itself is nothing new, and not the whole story. You need optical waveguides with bending radii much smaller than currently available for routing, and optical logic gates which are an even worse problem.
The article doesn't describe the technology -- is it electroabsorption? Mach-Zehnder?
Nevertheless, a small and fast silicon modulator has obvious commercial value, even if it isn't the greatest thing since sliced bread.
The difficulty with mastering tri-state and quad-state computers (as opposed to bi-state or binary) comes with the gates used. How would one perform an inverse operation when there are two other choices from which to choose? Instead of AND, OR, and NOT (not to mention combinations such as XOR, NOR, NAND, etc.), you would have at least 8 gates (if I recall correctly; I worked on something similar to this during the summer) doing things such as shifting, reversing, "inverting," and such. The different permutations of these make it even more confusing.
In addition to this, you would need to find a medium capable of carrying a tri-state signal (electrons are not best suited for this). In fact, due to the fact that we have a tough time determining on and off sometimes, I would personally suggest we leave it at binary for the time being.
I know it's a long post, but most of it is necessary.
Fluorescent and LED lights do not get hot.
Sure they do. They are far more efficient than incandescent bulbs, so they produce significantly less heat per lumen, but a very bright fluorescent or LED light can get quite hot.
In fact, high-brightness LEDs like the Luxeon Star have to be mounted on heat sinks to keep them from burning up.
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temperature, is really not the problem. The problem is stabilization. Different gates "stabilize" that is produce consitant output high or low at different rates, gates are strung together into circuits on the chip and thouse circuits then take a certain amount of time to stabilize, this is critical because the output of one circuit will be the input to another be it on the same IC or interfacing with something else. The reason you can overclock is in most cases ICs in computers the CPU in particular are underclocked to begin with. The clock cycle is longer then the stabiliation time when the chip is cool. However the voltage running though the traces and the swiches meets some resistence and part of it is disipated as heat, when silicon-eletric gates heat the respond slower and the stabilization time becomes longer, so the clock cycle must be longer if you want correct output. This is why if you take special meausers to keep the chip cooler you can often run it faster. Fiberoptics are not perfect and can heat too, the smaller you make them that problem is likely to exacerbate. The question I can't answer for you is wether that is a problem at all. silicon-optic gates may not vary in stabilization time in the same way that the electric counter parts do? They may and then the same rules apply or they could have some optimal temp where a cold chip does not work as well as a warm one? It might be they work perfectly up to a certain failure point?
I would love some answers form an engineer who is working with this stuff.
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It is a common misconception that electrons move quickly through conductors. This, however, is not the case. When an electric field is applied to a conductor (e.g. from a battery), the random motion of the electrons in the material gain a small drift velocity. In copper (a relatively good conductor), this drift velocity is on the order of 10^-5 m/s to 10^-4 m/s (much less than c=3E8 m/s). The reason that conductors work the way they do is that the information is carried by the electric field rather than the individual electrons. A good analogy here is to think of a tube filled with ball bearings. Stuff one more bearing in the tube at one end and one pops out of the other "instantaneously". While the inserted bearing didn't travel the distance, it did have an effect at the end of the tube.
Another common error is raised by the parent post. Transmission rate and bandwidth are completely different concepts. The transmission rate refers to the number of bits of information that can be transmitted down a pipe without loss (i.e. the capacity). Bandwidth, on the other hand, is a frequency domain concept and refers instead to the range of frequencies that the pipe can support. While it is true that a system with greater bandwith usually has greater capacity, it is a gross generalization.
Rapidly approaching the Zener knee...
After reading the article, it turns out that *all* this hoo-ha is about the fact that INtel has worked out how do do telecommunications level optical switching (read LED-LASER-RAPID-BLINKING) on a chip built using "normal" chip fabrication techniques.
This is in no way about "faster CPUs" it's ALL about "now we can fabricate telecomms equipment using standard CPU techniques, so they'll be cheaper and therefore easier to put into devices".
So you're not likely to be getting significantly faster PCs from this technology, though it *does* make more likely the chance of (one day) having a direct gigabit fiber port on your PDA (or digital camera/other-small-electronics-device)
Visit CryptoGnome in his home.
Not even LEDs are 100% efficient. However, for an optical system, the heat production is related to the duty cycle of the lamps, rather than the switching speed, so the heat production should remain constant regardless of clock speed.
That's true of the heat production in the guts of the lamp itself (at a given light intensity). But there are other factors.
On the one hand, this means you don't need to improve cooling to overclock. On the other, it means that you can't improve the overclock level with improved cooling.
Most of the heat loss in a circuit comes from the I-squared-R losses of the currents needed to charge and discharge the stray capacatance of the wiring (even the tiny traces on the ICs) and the space-charge of the devices.
In particular, if the wire has any significant length, you need to run that current through a series resistance (at least at the driving end) matching the impedence of the wire, in order to produce a nice waveshape at the far end and prevent "ringing" as the signal bounces back-and-forth (which would degrade the waveshape at the inputs to far-end gates and make the signal both more sensitive to noise AND more generative of noise to interfere with its neighbors.)
With CMOS you only pull power (except leakage power) when you CHANGE the state of a signal. But when you do, you have to charge, or discharge, the signal wiring through that matched resistance. The impedence of the wiring doesn't change a lot with technology and speed. So with a given length of wire, you have a given amount of energy dropped every time you switch it. Switch it twice as fast, generate twice as many pulses of heat.
New generations of semiconductors fight this in three ways:
- Shrink the components (so they have less stray capacatance to charge and discharge).
- Shorten the signal runs by making the components smaller so they can be closer together (reducing the stray capacatance of the lines). (But this doesn't help for signals that HAVE to cross the chip, or leave it.)
- Lower the power supply voltage (so you don't have to swing it as far. Current goes up with the the voltage, heat loss with the square of the current.) (For signals that leave the chip this may be harder to do than for signals that stay on it - due to external interference.)
For switching a light-emitting device you still have to charge and discharge the capacatance of the device itself and the wiring to it. Switch it faster and IT doesn't heat up much more. But the driver circuit does.
By putting a light modulator on the chip, Intel's new technology wins in two ways:
- You don't have to rapidly switch the power to the laser (which involves switching a LOT of current through an impedence-matching resistor).
- You don't have to run a microwave-speed signal through a long resistive wire, which degrades its waveshape and also produces still more losses.
Instead you switch a low-power, short-range, on-chip wire to a low-capacatance active region on the on-chip modulator. Switching losses are relatively small, comparable to those of a gate-to-gate internal signal in the same chip.
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