i/oZONE Products for the week of June 23, 2003
BitBlitz says . . .
Smart Shim - BitBlitz Announces a CX-4 Retimer that
Enables Low Cost XENPAK and X2 10GE Modules
Industry's First Fully Integrated Retimer For The Emerging
CX-4 Standard Also Offers Full XENPAK Register Compatibility
BitBlitz Communications is now offering the industry's first 10GE (Gigabit Ethernet) Integrated Retimer tailored to the emerging CX-4 standard. The BBT3821 uses BitBlitz's patented and proven CMOS physical layer technology (CoolPHYer) with very low jitter and low power, ideal for high port count Serial I/O applications.
The BBT3821 targets both module applications implementing the CX-4 electrical interface, as well as systems OEMs directly implementing CX-4. The solution is designed to have significant margin over the I/O performance requirements of the proposed CX-4 standard. CX-4 serves limited distance applications, targeting cables up to 15 meters in length. It also provides similar advantages for modules implementing the LX-4 standard, which provides for 1310nm optical solutions that drive up to 300 meters over multi-mode fiber.
"The CX-4 standard solves the very real problem of connecting multiple chassis cost effectively," said Jag Bolaria Senior Analyst at The Linley Group. "BitBlitz is enabling this new phenomena with a tailored device that meets the electrical requirements while enabling XENPAK register compatibility."
According to Bill Woodruff, vice president of sales and marketing at BitBlitz, "This solution extends BitBlitz's leadership in the retimer market, which the company pioneered with the introduction of its BBT3411 quad retimer last year." Our new solution includes features that enable implementation of a module with minimal chip count and cost, which are priorities for module designers."
Features & Benefits
The BBT3821 is designed for use in CX-4 modules and supports the MDIO interface
and registers required for the XENPAK/X2 interface. It also supports the
I2C interface required for accessing off-chip non-volatile memory. Additional
CX-4 friendly features include signal detect and its low 1.3W power dissipation.
The MDIO interface will directly support the required XENPAK/X2 registers.
The LX-4 implementation will utilize the I2C to also connect to the Digital
Optical Monitoring circuit.
The pinout and package of the BBT3821 have been chosen to further simplify
use in CX-4 based modules. The 17x17mm BGA package has a simple "thru"
pinout that aligns the pin assignments with a XENPAK connector on one side,
and the CX-4 on the other. This simplifies PCB design, lowers cost and increases
signal integrity. The primary heat path is through the top of the package,
which is ideal for module applications.
analogZONE Says . . .
With the introduction of its BBT3821 CX-4 retimer chip, BitBlitz has pulled off one of those classic end-run maneuvers and gotten out ahead of what appears to be a rapidly-growing market for XAUI-compliant short-haul 10-bit copper connections. Their chip provides a nearly-seamless shim between the XAUI interface used to drive expensive optical transceivers and a CX-4 electrical interface that can drive up to 15 m of low-cost Infiniband cable.
The reason this is a big coup is because most big iron being shipped today has sockets for XENPAK & X2 optical modules on their line cards, leaving XFP (long-haul) out in the cold - at least for the short run. BitBlitz recognized an opportunity in the fact that only a fraction of those line card interfaces (estimates hover around 50%) actually get out of the building in to long-haul single-mode fiber connections. Of the remaining half around 50% fall into CX-4 copper territory - i.e. under 15 m - a significant, and under-served market, especially considering that CX-4 is about one-quarter the cost of serial XENPAK.
So, all an enterprising module maker would need to get into the business of filling XENPAK sockets with low-cost short-haul modules would be a device that handles the signal timing and level conversion to the CX-4 format - right? Well, that's mostly true and it's what most other folks in the business are doing. But wait, there's more…
For one thing there is the fact that while the signals are similar between XAUI and CX-4, the physical sequence on the connector is not. By carefully designing the two pinouts to avoid crossovers when connecting to their respective connectors, BitBlitz lets manufacturers use a three or four-layer PCB instead of a half-dozen layers or more. A small detail that makes a big difference.
Another small but important detail is that XENPAK modules are configured using the MDIO serial interface, while CX-4 and the emerging LX-4 (the 4-lambda intermediate distance multi-mode fiber connection specification) use the I2C interface protocol. That's where BitBlitz comes in by providing a direct MDIO/I2C interface conversion. This allows the 3821 to converse with either the non-volatile memory (NVM) format used by a CX-4 and LX-4 modules to configure their registers, and talk to the digital optical module (DOM) support registers used in LX-4 applications (See figure). This eliminates the microcontroller normally required to configure a reworked XAUI part for this special application.
While CX-4 applications should be the mainstay of the initial business for these parts, the emerging LX-4 module may make an equally attractive socket for this part. LX-4 gets around the distance limitations for 10-Gbit/s optical links over multi-mode fiber (the kind found in most buildings these days), which gives you a maximum of 26 m with serial XENPAK transceivers before dispersion takes its toll. The emerging LX-4 standard allows the use of installed MM fiber by sending out four 2.5 Gbit/s streams on four separate lambda centered at 1310 nm.
While the optical link application looks promising, I'll reserve my unbounded enthusiasm here as it's mostly speculative at this point, and subject to the whims of the wily end-user. I'm gun-shy about situations like this since Broadcom found itself on the wrong end of a similar bet back in the Fast Ethernet days. They assumed everyone would want to run 100-BaseT4 Ethernet over the four pairs of existing Cat-3 wire that was pulled in 65-70% of the buildings at that time and brought out a fancy 100BaseT-4 transceiver that I reviewed. I enthusiastically agreed with them that 4-pair Cat-3 would accrue a large market share in existing wire plants, and looked rather foolish when 100BaseT over 2-pairs of Cat-5 won the day.
In any case, I think BitBlitz has a winner here for CX-4 applications. It may even slow the development of 10-Gig Serial copper interfaces by driving the cost of a quad-2.5-Gbit/s solution down to the commodity level.
BBT3821 samples will be available in July 2003 through the BitBlitz network
of manufacturing representatives, distributors and direct from the company.
They are priced at $60 in 1000-piece lots.
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