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New processes push technology to the verge of commercialization

International Business Machines, Inc. (IBMis among the companies racing to develop nanophotonics -- on-die light based signaling components -- which can be incorporated directly side-by-side with traditional silicon-based electronics using traditional manufacturing techniques like complementary metal-oxide semiconductor (CMOS).

Currently, signals between components like the processor cores and the memory crawl along as electrons along copper-based wires.  In the new scheme modulators (which create the signal, often using a ring), wave-length multiplexers (which route signals), switches (which turn signals on or off), and detectors (which receive signals) are baked onto silicon chips connected by fiber optics.  Signals then travel at the speed of light along fiber optic channels.

After first demoing the technology in crude proof-of-concept form back in 2010, IBM has returned with the world's smallest announced CMOS-compatible nanophotonics processes.  The company showed off chips this week that were build on a traditional 90 nm CMOS node, a node far smaller than earlier prototypes.

IBM wave guide
Blue optical wires are shown accelerting the "slow" copper wire (orange) traffic.

IBM says the technology is "primed for commercial development" and will soon be ferrying "terabytes of data between distant parts of computer systems".  In a demo IBM showed off 25 gigabytes-per-second (GBps) transfer rates, a speed typically seen in bulky telecommunications fiber-optics equipment, not in PC interconnects, which crawl along at megabytes-per-second (or around 1 Gbps for high-speed PCI-express lanes).

The hope is that the new interconnects will soon pump internal and external communication up to speeds of up to thousands of times the current technology.

Dr. John E. Kelly, Senior Vice President and Director of IBM Research, remarks, "This [latest showcased] technology breakthrough is a result of more than a decade of pioneering research at IBM.  This allows us to move silicon nanophotonics technology into a real-world manufacturing environment that will have impact across a range of applications."

The IBM research fellow and SVP will be showing off his work in a paper at the IEEE International Electron Devices Meeting (IEDM), which is being held this week in San Francisco, Calif.

Sources: IBM [1], [2]

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By CityZen on 12/10/2012 1:13:46 PM , Rating: 2
In a demo IBM showed off 25 gigabytes-per-second (Gbps) transfer rates, a speed typically seen in bulky telecommunications fiber-optics equipment, not in PC interconnects, which crawl along at megabytes-per-second.

Wait! what? PCIe v3.0 bandwidth is already in the 1 GB/s range, per lane (16 GB/s for a 16 lane slot), and v4.0 will be double that.

RE: Bandwidth
By KentState on 12/10/2012 1:19:48 PM , Rating: 3
Every lane would be 25GB/s. Hopefully fewer lanes would lead to less complex motherboards.

RE: Bandwidth
By Egglick on 12/10/2012 1:40:55 PM , Rating: 2
Yeah, a single 25GB/s lane would be enough for most any current consumer-level addon card. The biggest benefit would be to the System RAM though. This sort of technology would both drastically increase bandwidth, and also lower latency to almost nothing. You could theoretically see system RAM which comes close to the speed of the CPU's onboard cache.

RE: Bandwidth
By jdietz on 12/10/2012 4:13:04 PM , Rating: 2
No it won't. It'll be closer to being a "true" L4 cache.

Modern system latency:
Register: Next cycle
L1 Cache: 4 cycles (Ivy Bridge)
L2: 12 cycles (Ivy Bridge)
L3: 24 cycles (Ivy Bridge)
RAM: 133 cycles (Ivy Bridge @ 3.4GHz)

This tech may help reduce RAM latency. Not sure exactly how much. Other tech might help more at reducing latency, like phase-change RAM.

RE: Bandwidth
By Egglick on 12/10/2012 6:17:35 PM , Rating: 2
Of course I'm not talking about using existing DRAM technology. You would want to design something entirely new in order to take advantage of the exponentially faster interconnects.

RE: Bandwidth
By Digimonkey on 12/10/2012 6:47:08 PM , Rating: 2
Is that really the case? You usually don't measure a serial connections in bytes.

RE: Bandwidth
By Digimonkey on 12/10/2012 6:51:13 PM , Rating: 2
Nevermind, I see it was meant to be 25 Gigabits.

RE: Bandwidth
By kingmotley on 12/10/2012 1:52:18 PM , Rating: 2
You are correct that PCIe v3.0 bandwidth is currently ~8Gbps per lane (over copper).

However, this technology is ~25Gbps per transceiver, over fiber. And multiple transceivers can be used on a single fiber. You could conceivably multiplex all 16 "lanes" into a single fiber with this that would have ~3 times the bandwidth, and all the benefits of a single fiber (longer runs, less signal degradation). Of course you could also run multiple fibers. Think 16 fibers running 16 channels, each 3 times as fast as a single PCIe v3.0 lane.

** I used 16 channels as an example that could be multiplexed, but I didn't see a limit from the story. It could be anywhere from 2 to a jillion for all I know.

RE: Bandwidth
By Argon18 on 12/10/2012 3:42:59 PM , Rating: 2
At least with current telecom WDM, 16 colors is commonplace, and 256 colors is getting popular.

You're right in that the theoretical limit approaches infinity, since there are an infinite number of color variations in the visible light spectrum, and that doesn't even include infra red or ultra violet combinations.

Of course in practical terms however, it's a matter of diminishing returns, as the more colors you use, higher grades of optical fiber are required that accurately transmit the light without distortion or db loss, and more sensitive transceivers are required to pickup the signal at the other end. At a certain point, it becomes cheaper to just lay another physical cable.

RE: Bandwidth
By bobsmith1492 on 12/10/2012 4:45:01 PM , Rating: 2
It doesn't approach infinity; the standard RF bandwidth limitations apply. Of course there is a ton more spectrum available than in the RF range.

RE: Bandwidth
By Jaybus on 12/11/2012 11:53:33 AM , Rating: 2
I think the point of this technology is being overlooked. The point is not exactly a cheaper version of the i/o over fiber optic technology we already use. It is replacing the electronic bus connecting one chip with another, for example a memory channel or QPI. More yet, it is about connecting together multiple chips so that they may act almost as if they are a single monolithic chip by making the latency and bandwidth of chip-to-chip links comparable to on-die links.

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