interconnects.
Hey man, good point once in a while! Sure I want to have nothing in common with Muslim fundamentalists, so much so that I would not even share the planet with them if only there was any way to do so other than suicide ;-)
NNN
Good grief, this was the #1 headline article on the front page of today's SF Chronicle.
The "science" writers of the world seem to be copying and embellishing one another's articles; they keep gatting more absurd.
Nobody has mentioned about the size of optical waveguides, cutoff wavelengths and stuff. Copper and aluminum conductors are already down to 50 nm width; the light from these lasers is, what, 1300 nm?
John
Optics is perhaps practical for long wires (1 cm or longer). Those connections have to be made at the top metal levels, which are typically
2 to 5 um pitch. Wiring density with optics is comparable or slightly better, because you don't need differential signalling.Cheers,
Phil Hobbs
So you can do dwdm or at least WDM using a single laser? Or is it more LED? How is the cavity for the laser formed? VCSEL?
-- Del Cecchi "This post is my own and doesn?t necessarily represent IBM?s positions, strategies or opinions.?
No, you use add-drop couplers made from resonant rings coupled to the Si waveguides. You can make modulators that way too--you tune the ring back and forth across the laser line.
Cheers,
Phil Hobbs
I'm referring to the hype about how 'optical computers' will be 1000x as powerful using 'this new technology' BS.
-- Dirk http://www.onetribe.me.uk/wordpress - The UK\'s only occult talk show Presented by Dirk Bruere and Marc Power on ResonanceFM
"If they can pull it off, it will definitely make circuits work faster," Hutcheson said. "It'll make your PC work faster. You can edit movies. Photoshop will work much easier."
- San Francisco Chronicle
John
But it won't make it work faster than simply shrinking size to the next gen semi process.
-- Dirk http://www.onetribe.me.uk/wordpress - The UK\'s only occult talk show Presented by Dirk Bruere and Marc Power on ResonanceFM
Do you think that on-chip optical links will ever make sense? A laser and a photoreceiver seem like a lot of overhead to move signals a cm or so.
Fast serial inter-chip links seem a little more practical, but they will still need a fast, low-noise receiver and connectors. Equalized electrical connections keep getting better... somebody just demonstrated a 10 GBPS link that works over a couple hundred feet of unshielded CAT6.
Fiber is great over distances where electrical losses get untenable... hundreds of meters or hundreds of km.
John
interconnects.
For >30 years I've been "proven" wrong. There's a difference between proof of concept and a viable economic, marketable solution... which seems to get lost on you.
Go ahead - I'll be delighted to not have your mindless ravings to deal with.
-- Rgds, George Macdonald
With imagination like that, they could be running a major software company.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I think that optics will continue to move in from the long-distance end toward shorter and shorter links, but how far it gets is anybody's guess. You're right that the wire guys are smart, and that wire can still be improved quite a bit. (In fact one of the main problems I see is that the board-to-board stuff is all 850 nm multimode, whereas the on-chip stuff is shaping up to be 1.55 um single mode, polarization preserving, for good reasons of material absorption and manufacturability in both cases. In reality the gazinta has to connect with the gazouta.)
The difficulty with equalizing electrical links--pre-emphasis, decision-feedback equalization, etc.--is that it eats power. Since the wire attenuation is what it is, that 10 Gb/s Cat6 link has to work by beating the daylights out of the near end so that something vaguely recognizable can come out of the DFE at the other end. You can't do that on chip, because you need thousands of those links (just counting the long ones), and want to keep the interconnect power below, say, 30W. Putting a lot of EQ on also requires higher supply voltages.
Wire has some clear limits. The capacitance of a copper wire is going to be 2 pF/cm forever and ever, and you aren't going to improve the conductivity of copper either. Damascene processes (where the copper sits in a liner of refractory metal) make this worse by reducing the cross sectional area of Cu. You probably can't make reliable electrical links with less than 200 mV of differential swing. That means that wire bottoms out in the 1 pJ/bit range, whereas optics can potentially get below 50 fJ/bit. We think that the crossover comes around the 32-nm node.
If you have the chance, take a look at the current ITRS technology roadmap--it has charts of the technologies required for each node, and the boxes are colour-coded green, yellow, or red. The interconnection section of the 32-nm node is solid red, meaning that nobody has a clue how to do it, despite having beaten on the wiring problem for decades. That means that optics is a good contender to be the long-wire interconnection solution for 32-nm and 22-nm.
As you say, it won't happen with garden variety optical links--which is why it's a fun area to work in.
Cheers,
Phil Hobbs
On Tue, 19 Sep 2006 10:41:33 GMT Jan Panteltje horked up in vomit id: :
*giggle*Angels? Do you believe in the Tooth Fairy and Easter Bunny too?
The irony, one of many, is that increased compute power has almost always made computers less reliable and harder to use.
John
I don't believe in usenet trolls, but there you are.
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
Like yesterday's foxtrot cartoon. The kid is creating a website, and he's bragging about everything he is using to create it. His sister asked, But what will it look like? He has no idea. I think we've found the person responsible for creating all those useless websites for semiconductor manufacturers.
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
With quite a bit of room to spare, I might add.
How about the Great Pumpkin? Do you think Linus will ever give up his annual foray into the pumpkin patch, or is he doomed to a lifetime of heartbreak and disappointment? EMWTK.
:
Ask Eeyore. He's the expert on cartoon characters.
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
This isn't just waveguides on a chip, they've also added a light source right on the chip. That part is different. Most light-emitters are incompatible with silicon.
Mark
They glued individual compound-semiconductor lasers on top of a silicon chip. Cute, but it hardly deserves front-page headlines. And all of the press articles I've seen so far have been loaded with technical inaccuracies and absurd projections. Intel has a fondness for this sort of thing, and "science writers" rarely know anything about what they are writing about.
John
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