Marvell, a technology leader in the development of extreme broadband communications solutions, today announced a significant industry breakthrough with the world's first 10 Gigabit Ethernet operation over 15 meters of standard 24 gauge copper cable using the Company's Alaskaý X 10 Gigabit Ethernet XAUI SERDES IC. This accomplishment paves the way for significantly lower cost 10 Gigabit Ethernet links for applications requiring high-bandwidth links for distances up to 15 meters.

This breakthrough allows copper cable to be used for 10 Gigabit Ethernet applications such as interconnect links between stackable switching systems, 10 Gigabit Ethernet uplink connections and chassis-to-chassis connections. Today, optical links are the most commonly used form of interconnect for these applications. The cost of optical links is significantly higher compared to copper links because the optical links constitute several additional optical and electrical components. While the use of more active components often results in reduced reliability of the optical connections, the use of copper cable will allow systems vendors to offer a highly reliable and lower cost alternative to optical solutions for short distance applications such as stacking links between switch systems.

Marvell achieves reliable 10 Gigabit operation over 15 meters of standard InfiniBandý 8-pair cable with 24 gauge copper wires. Choosing a standardized cable and connector such as the InfiniBand cable eliminates the need for expensive proprietary cables and further reduces costs. In addition, the use of 8-pair cable allows for an aggregate bi-directional bandwidth of 20 Gb/s using IEEE XAUI signaling, which is based on 4 pairs each in transmit and receive directions at 3.125 Gb/s with 8B/10B coding.

"Marvell's engineering excellence has once again been demonstrated with this industry breakthrough. This revolutionary achievement will provide tremendous cost savings for next-generation switching systems, supporting Gigabit to the desktop with 10 Gigabit stacking and uplinks," stated Gary Smerdon, Marvell's VP of Marketing for the Communications Business Group. "We plan to demonstrate 10 Gigabit operation over 15 meters of copper cable at the NetWorld+Interop tradeshow in Las Vegas from May 7th-9th and at the Supercomm tradeshow in Atlanta from June 4th-6th (booth numbers 8085 and 24822, respectively)."

Hewlett-Packard Company has been leading the industry toward the development of a low-cost copper interconnect for 10 Gigabit Ethernet. "Stacking and clustering connections often involve distances less than 15 meters, which makes copper cable the most desirable medium for these applications," said Dan Dove, Principal Engineer, HP Procurve Networking.

"The need to provide 10 Gb/s uplinks or stacking capability over copper cabling will become an important low cost alternative over optical, especially as end-users continue to deploy high-density Gigabit Ethernet switches within shorter distances of one another," said Sean Lavey, an analyst with IDC. "We find that networking OEMs will adopt this technology to interconnect not only high port density standalone switches, but also large multi-shelf chassis system designs."

The Marvell Alaska X transceiver uses sophisticated signal processing and circuit design techniques to achieve the 15 meter milestone. The Alaska X device uses programmable transmit pre-emphasis signal processing technique to compensate for inter-symbol interference (ISI) caused by the copper media such as PCB traces and cables. The Alaska X chip also features flexible amplitude adjustment capability. Programmable amplitude coupled with flexible transmit pre-emphasis yields reliable operation over high loss and high distortion environments such as 15 meters of unequalized copper cable. In addition, the Alaska X transceiver features unparalleled low transmit and receive jitter, which provides extra timing margin resulting in enhanced overall performance and extended transmission distances.

The Marvell Alaska X device, the 88X2040, is the industry's first 0.15 micron CMOS 10 Gigabit Ethernet XAUI Quad 3.125 Gigabit SERDES. The Alaska X device features the lowest power, the highest performance and the smallest form factor solution on the market today. The 88X2040 transceiver incorporates all of the necessary functions to implement the Physical Coding Sublayer (PCS) and Physical Medium Attachment (PMA) functions as specified in the latest 10 Gigabit Ethernet IEEE 802.3ae draft, while achieving very low power dissipation of 1.3 Watts.

The Alaska X device incorporates four transceivers operating up to 3.125 Gb/s, each with a selectable 8B/10B encoder/decoder. The four transceivers can operate at 1.0, 1.25, 2.0, 2.5, and 3.125 Gb/s to support a variety of backplane applications. Further, the Alaska X transceiver performs clock and data recovery and de-serialization for the receive path, as well as pre-emphasis, serialization and clock generation for the transmit path. The Alaska X device utilizes lower rate clocks as reference for internal clock generation. The device also allows for the use of either 62.5, 125 or 156.25 MHz reference inputs to provide flexible clocking.

The parallel interface on the Alaska X device is a 10 Gigabit Media Independent Interface (XGMII) as specified by the IEEE standard. In addition to the latest IEEE XGMII HSTL I/O support at 1.5V, the Alaska X transceiver features support for XGMII connection to legacy ASIC devices using HSTL I/O operating at 1.8V. For 10 Gigabit Ethernet optical applications, the device connects to optical modules such as the XENPAK using the XAUI interface and to 10 Gigabit Ethernet switch devices using the XGMII interface.

Marvell Semiconductor, Inc., 700 First Ave., Sunnyvale, Calif., 94089; Tel: 408-222-2500, Fax: 408-752-0588. Web: www.marvell.com.

Marvell offers higher layer protocol processing capabilities with their Ethernet switches and WAN controllers. In January 2002 they added the wireless 802.11b, all CMOS, RF and baseband devices. They integrate the power amps, VCOs, and LNAs into a single chip for the RF and have a baseband device as well. The next step for the company will be to integrate the MAC and baseband for a 2-chip solution.

In September 2001, Marvell introduced the Alaska X - a 10Gb quad SERDES device. Since then they announced the ability to drive up to 60 inches of FR4 backplane material through 8 connectors and added 3.125 Gb per channel. That's significant when you consider that maybe no one else has demonstrated the ability to drive more than the 20 inch range over standard backplane material.

Now, Marvell is introducing another product based on the 10Gb/s SERDES, in an Ethernet device. This is not only important for this device but it is important because it is a technology invented for switching devices. The company tested the Alaska X device with standard piggyback cables and achieved successful results for connections of 15 meters.

When gigabit to the desktop happens in the near future, the uplink or aggregation links will also need to move to 10Gb/s. Today, the basic link is optical. However, there are many applications that need a short connection, such as a stacking application which may need only a 2 meter connection. Optical is good for connections of 200 meters, 10km or even 40km. But it is an expensive solution for short distance connections.

The expensive nature and the interest from customers for an alternative to optical connections was reason enough for Marvell to investigate a solution. In Ethernet there are two form factors. One is modular, which is a chassis-based system with a backplane that connects the boards together. The other is a fixed-form factor with 1u to 2u high boxes stacked atop each other and connected with cables. The advantage is that the boxes act as one unit and they are easy to manage. The high speeds between these boxes is easy to manage and has a minimal cost because you don't have to add the Ethernet MAC and go through initial protocol processing, from one box to another. Described another way, SERDES technology is the ideal way to hook device-to-device without a PCB. Otherwise, you have to use uplinks that connect to another switch and will require a separate control.

The block diagram of the device shows how it works like 4 independent channels for proprietary communications. Customers can use standard link serializers and have four of them linked independently or they can have the device be one large 10Gb/s data stream - which is how the IEEE Ethernet Standards Committee requires that they work.

Figure 1 : Block Diagram
Click for entire image

The Alaska X product uses a signal processing techniques that allow it to be used with copper cable. These same signal processing techniques are not needed in the optical environment to transmit a regular NRZ signal with 1's and 0's. However, copper requires a technique called transmit pre-emphasis, which helps compensate for the inter-symbol interference distortion, caused by copper on the printed circuit boards, PCB traces or copper cable.

The signal processing technique attenuates the high frequency of the signal more than the low frequency content of signal, causing the eye pattern on the oscilloscope to close. The figure shows what the eye pattern looks like before (left) and after (right) the signal is attenuated.

before

after

Figure 2 : Eye pattern comparison
Click for entire image

The pre-emphasis is done to boost high-frequency content energy, or it is used to lower the low-frequency content of the signal. It equalizes the energy of the high and low frequency portions of the spectrum, and thus gives it a clean receive eye pattern. The clean signal allows the Marvell product to communicate over long traces or cables. In addition to pre-emphasis the amplitude adjustment capability allows the Marvell Alaska X to change the drive strength to drive different lengths of copper wire. Additionally, the jitter is low so the resulting eye pattern on the receive end is not closed.

For example, imagine you have signal with 101011. Traditional pre-emphasis is thought of as an overshooting of the signal. Marvell doesn't use this technique because it causes EMI problems. The technique Marvell uses transmits the 1010 portion with no change to the signal. But for the last 11 of the signal they transmit the first 1 as a 1 but the following 1 is de-emphasized (transmitted with lower amplitude) because it causes a problem with the low frequency portion of the spectrum. You can find more information on this topic from ChipCenter's Networking Knowledge Center.

This is well-timed product that the market is ready to use now. Presently, in-building architecture has wiring closets from floor to floor stacked directly on top of each other. Then they have big holes to run the cables from floor to floor. The 15 meter limit on cables is long enough to go from wiring closet to wiring closet between two floors. Anything longer than 15 meters and you should probably use an optical connection, which can hook directly into Alaska X device.

If you look at the cost comparison, standard optical connections cost between $2k - $5k dollars for one link. Copper connections like the one from Marvell cost about $200 - $300 dollars.

Another less obvious difference between optical connections and copper connections is the number of active parts. Optical connections have more active components in the link. They have four more active components including the laser and the photo diodes on each side of the connection. Reliability goes down exponentially as you put more active components together, so an optical system is inherently less reliable than a copper system. Finally, optics require expensive test equipment and specially trained technicians to handle the lasers and clean the lenses. Copper has no such requirements.

A data sheet was not available when this product was reviewed.