Optical components

Velio Accelerates to 6.25-Gig

Velio Communications Inc. today announced it's managed to send a 6.25-Gbit/s signal successfully over copper -- a feat that would put Velio on a par with the highest speed offered by Accelerant Networks Inc..

But wait -- there's more. The announcement is signficant in that Velio is the first to get a pure 6.25-Gbit/s stream to work across copper lines. Accelerant's product actually doubles up the bits on a 3.125-Gbit/s signal. But more on that later.

Why are high-speed, copper-based chips needed? The goal is to allow system OEMs to increase backplane speed without having to rebuild boxes with more expensive fiber connections. Copper-based backplanes run comfortably at 2.5 Gbit/s, but if there were a way to send signals across that same backplane at 5 Gbit/s or even 6.25 Gbit/s, that would allow an OEM to increase speeds simply by replacing line cards with new versions with faster SerDes (serializer-deserializer) chips.

Accelerant has been making noise about 6.25-Gbit/s backplanes, including a deal to put the technology into Agere Systems Inc's (NYSE: AGR/A) ASICs (see Agere, Accelerant Team Up). Velio hasn't chimed in at that speed until now.

It's always been possible to send high-speed signals across copper traces, but the signal gets noisier as the speed increases, eventually dissolving into gibberish. Using various tricks of analog electronics, chip makers have reached a point where 2.5-Gbit/s backplanes are commonplace. More recently, they've made a safe bet out of 3.125-Gbit/s signals, which every high-end transceiver company is offering.

Here we come to the core difference between Accelerant and Velio. Accelerant's chips don't actually send 6.25-Gbit/s signals. Instead, they talk at the relatively safe 3.125-Gbit/s speed, using an encoding trick called PAM4 to "double up" the bits -- they do so by having every clock pulse carry two bits rather than just one. So Accelerant gets 6.25 Gbit/s worth of data out of a 3.125-Gbit/s signal.

Velio does it the hard way, and they're proud of it. In today's announcement, officials say they've managed to get a pure 6.25-Gbit/s stream to work across copper lines, something no commercial product has done to date.

Velio's trick lies in pre-emphasis -- an intentional distortion of the signal before transmitting it.

Pre-emphasis cancels out the distortion of signals, in which a particular "0" or "1" bleeds into a neighboring clock cycle. Quite a few companies use "one-tap" pre-emphasis, which means the chip corrects by looking forward and back one clock cycle. To get to 6.25 Gbit/s, Velio's upping the ante to three taps -- looking ahead and behind by three bits.

"I'm not aware of anybody else doing three taps of pre-emphasis," says Bill Woodruff, Velio vice president of marketing.

The technology will show up as a new version of Velio's GigaCore products by the end of the year, Woodruff says.

As for the PAM4 approach, Woodruff says Velio's not interested.

"PAM is cute. PAM has its good attributes. But the baggage you carry when you do PAM is die area [i.e., chip size] and power," says Woodruff. "When you start to go to 16 or 32 channels, the baggage of PAM gets in the way." Accelerant declined to comment for this article.

Accelerant has hoped to gain market strength through its recent deal with Agere, giving Agere permission to integrate the Accelerant SerDes into an ASIC, either for internal use or external sale. Agere also will be a second source for Accelerant's chips, a relationship that gives some reassurance to OEMs that might be skittish about semiconductor startups.

The deal arose as Agere's ASIC customers started asking about Accelerant's SerDes. "We have many of the same customers, and the customers did the initial matchmaking," says Cindy Genther, Agere's director of marketing.

This kind of intellectual-property licensing is commonplace in semiconductors, practiced heavily by the likes of Rambus Inc. (Nasdaq: RMBS) (see Rambus SerDes Hits 10-Gig).

But Rambus licenses to pretty much anybody, whereas Accelerant is working only with Agere. "We're not in the intellectual property licensing business," says Jim Tavacoli, Accelerant vice president of marketing. "We are a small company. We wanted to enable ASIC integration with minimal impact to our resources."

— Craig Matsumoto, Senior Editor, Light Reading
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BobbyMax 12/5/2012 | 12:37:17 AM
re: Velio Accelerates to 6.25-Gig Velio has enormous advantage over Accelerant because of its with Agere. The market for gigabit Ethernet over copper is not that big. To be useful the signal has to travel long distances. The early applications of Gigabit over Ethernet would be in the enterprise. The other applications may be: Switch to switch communication, switch to server communication.

TheNet 12/5/2012 | 12:37:16 AM
re: Velio Accelerates to 6.25-Gig BobbyMax,

Velio's product are copper backplane transceivers.

DaCrusha 12/5/2012 | 12:37:07 AM
re: Velio Accelerates to 6.25-Gig Limited applications?

Like perhaps every new switch backplane designed from now until 12.5G is here! Provided of course that the backplane can be built with reasonable materials and the chassis needs this much throughput. (Although I can't imagine anyone would build a new Backplane that would provide less than a 10G link to a line card).

Accelerant's chip was designed to get more life out of existing FR4 backplanes by cranking up the data throughput from 3.125Gbs to 6.25Gbps.

If Velio has that same goal (using FR4) and it's test was running on FR4 (for more than 4") then it is quite an accomplishment.

Now, if we could only find some 10G backplane connectors to build with.


PS: BobbyMax,
If you don't know what the parts are for it is ok to just move on and read other things. Do not feel pressure to start a discussion just because you understood a little about what the article was talking about.

It would only take a few minutes to look up one of these Product Briefs to get a good picture of what they are trying to sell.

dljvjbsl 12/5/2012 | 12:37:04 AM
re: Velio Accelerates to 6.25-Gig The world is awash in unsaleable bandwidth. Can anyone tell me why there is excitement over new devices which will enable more bandwidth?

This is a real question and not a sarcastic remark.
gea 12/5/2012 | 12:37:04 AM
re: Velio Accelerates to 6.25-Gig Booby:

I have accused you before of not getting any information outside of the Lightreading articles. Then I accused you of not reading the articles very carefully. Now it is obvious you did not even read past the first paragraph.

Aside from being crazy and a moron, you're unbelievably lazy. Between this and your comment this morning about CWDM in response to a Tellabs cross connect, I really wonder what passes through your mind as you post. Since you understably have ZERO credibility on these boards, why don't you just stop posting?
billy_fold 12/5/2012 | 12:37:03 AM
re: Velio Accelerates to 6.25-Gig Awwwah. If he stopped posting, it would take away all the fun and my laugh of the day. (Is he really serious?)

DaCrusha 12/5/2012 | 12:37:02 AM
re: Velio Accelerates to 6.25-Gig dljvjbsl,

How bout getting the same amount of system bandwidth from a box that is 1/8 the size and 1/4 the cost of what is available now?

You could build a new system (or re-build an old one) in a smaller footprint, with higher throughput, lower power consumption, more features, etc. All because an old 64 bit parallel bus that was designed 5+ years ago (the best of which topped out near 6.4Gbps) has become "2 differential pairs", 4 wires! Make it 8 wires and you've got a 12.5Gbps full-duplex link and the bottle neck of the shared bus is no more.

Or were you talking about bandwidth in something like "dark fiber"? (Which is another story, but not totally un-related).

gea 12/5/2012 | 12:37:02 AM
re: Velio Accelerates to 6.25-Gig "The world is awash in unsaleable bandwidth. Can anyone tell me why there is excitement over new devices which will enable more bandwidth?"

Yo! Did you actually READ this article? It's about a backplane! Hello!

OK, let me take a Xanax and calm down. First of all, this "bandwidth" can't be sold: it's an increase in the backplane bandwidth for networking systems. What it will (can) do is allow for new telecom systems designs that can connect a whole s-load of cards to another s-load of cards. Thus, you could build bigger, cheaper (and physically smaller) cross connects, or possibly have a better God box (ie, you could have a SONET cross conect in the same box as an ATM switch as an IP router, simplifying (for instance) IP-over-ATM-over-SONET architectures).

As for whether anyone will actually buy this product, I don't know. But it has only an indirect relationship to actual service transmission bandwidth.
wild_thang 12/5/2012 | 12:37:02 AM
re: Velio Accelerates to 6.25-Gig Because its not about bandwidth of the product, its about bandwidth in the backplane. This means you can pack more into less space (i.e. cheaper and smaller boxes), not necessarily add bandwidth to the product but pack more bandwidth into smaller package. Or upgrade to more bandwidth without a backplane change (in theory).
rabidfruitbat 12/5/2012 | 12:36:59 AM
re: Velio Accelerates to 6.25-Gig before everyone gets excited over the arrival of a 6.25Gbps binary serial links, they should check the cost of designing a system / board that uses such links.

The number of people who can do 6.25Gbps is very small and you have to show them the bags of money before they come talk to you. This is the down side of Velio's solution. The number of people who can design and layout systems / boards with 3.125Gbps links is relatively small but you can hire or contract them to do the work. This is the advantage of Accellerants solution, it has a frequency of 3.125GHz.

In todays environment you don't want to spend more money on development than you have to.

However there is a down side with Accellerant and that is there are no standards for PAM4 signaling so you potentialy have a single vendor solution.
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