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connectivityZONE Products for the week of November 7, 2005
Texas Instruments Says…
Texas Instruments now shipping PCI Express-to-PCI
bridge
New device enables transition from legacy products to latest
PCI Express applications and support longer distances
Texas Instruments Inc. has announced another addition to its PCI Express
product line with the availability of a new PCI Express-to-PCI Bridge. The
XIO2000 allows seamless bridging between legacy PCI devices to the latest
PCI Express applications used in PCs, docking stations, ExpressCard, split-chassis
systems, and test and measurement instruments.
TI's new bridge device (XIO2000) is fully compliant to the PCI Express to PCI/PCI-X Bridge Specification, Revision 1.0, which is critical for interoperability with other PCI Express applications. The XIO2000 also supports longer trace lengths than competitive devices, allowing designers to support longer distance PCI Express endpoint devices without the loss of signal strength.
"The XIO2000 allows customers to bridge their existing PCI application to the newer PCI Express architecture without having to worry about compliance and interoperability issues," said Jawaid Ahmad, product marketing manager for TI's Interface Business Unit. "Prior to release we did extensive validation and testing to ensure customers get a compatible device to use with the plethora of add-in cards and root complex devices available in today's market."
The device has a x1 lane upstream port connection to PCI Express root
complex, providing support for up to six x1 PCI endpoint devices on its
downstream side. By using TI's XIO2000 customers are now able to expand
one x1 PCI Express lane to support up to six devices.
analogZONE Says . . .
TI's XIO2000 PCI/PCIe bridge chip is well-timed to serve the many transitional applications that are arising as PCIe begins its almost inevitable domination of desktop, laptop, and server applications. In some ways this part it not "news" since earlier versions have been demoed and sampled for a year ago, but this is its first widespread commercial introduction. TI wisely invested that year of field testing this bridge to ensure full interoperability with all "Tier 1" chipsets and most of the leading PCIe add-in cards currently on the market. This, and a few other interesting features, may help the XIO2000 distinguish itself from the very respectable competing solutions introduced earlier by PLX and other traditional I/O players.
Like its competition, the XIO2000 bridge meets PCIe 1.0a specs, and supports 32-bit, 32/66-MHz PCI busses. But TI has provided a few value-add features like integrated bus PCI arbiter logic and clock buffers that will help trim BOM costs. Designers will also appreciate its LocalBus circuitry, which has been engineered for low latency and to deal with timing issues when transitioning PCI/PCIe and switch fabrics.
TI also takes a leadership position by offering integral adaptive equalizers on the PCIe transceivers, something which enables longer (up to 2x) the reach on mother boards or backplanes, as well as the soon-to-be approved cabling that basic line drivers can provide. The extra reach will be especially useful in new split-chassis PC designs which promise to hide the bulky CPU and unclutter desktops with little more than a monitor, mouse, keyboard, and a small interface panel for USB and other critical I/O connections. They were quite reluctant to discuss the details of the adaptive equalizer used in this product but I am relatively confident that much of its technology is derived from the 6.25 Gbit/s SerDes and the XAUI transceiver I reviewed back in the Spring of 2004.
TI was also not forthcoming about the part's operating power, although they were happy to tell me that the bridge supported a full suite of advanced PCIe power management features. To be fair some of this reluctance comes from the fact that the power consumption of any properly-engineered bridge device will vary significantly according to how heavily its busses are loaded. But regardless of whatever power consumption figure they do finally release, it will be interesting to contrast that to PLX's claimed "under500 mW" level. Since PLX does not specify whether this is a maximum or average figure, I suggest you get a few more facts before making a direct comparison.
The bridge also supports PCIe's optional clock dithering mode (spread spectrum) when it's configured in the common clock mode. While it's not currently in heavy use, spread spectrum clocking may be a good option for EMI control in many products where shielding is overly costly or impractical.
In conclusion, TI's introduction of the XIO2000 is timely and welcome. It's most likely bridge products like this will only enjoy a heyday of 2 - 3 years until most ASSPs and ASICs have native PCIe capabilities. But they will sell like hotcakes during this transition period as they find places in adapter cards to update legacy systems and in new products where key system elements still lack PCIe interfaces. After this initial "gold rush," sales should continue at a more modest pace to support upgrades to embedded systems which have much longer product life cycles and in applications requiring a straightforward, low-cost bridge to IEEE 1394 connections.
The current pricing is appropriate for low-volume embedded applications where markups are higher, but TI will have to trim it substantially to enjoy sales in mainstream PC products. I am almost certain that TI's aware of this and will make the necessary adjustments as market forces demand.
The XIO2000 PCI Express-to-PCI Bridge is in production in Microstar BGA-201 priced at $14.95 in 1000-piece lots.
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