Intel pushes serial bus

Last month, attendees at Intel Developer Forum (IDF) got their first up-close look at PCI Express. Intel demoed a new chip based on the technology that some analysts believe will fully develop in 2004 and flood the market in 2005. But it's not certain where PCI Express might ultimately play. Let’s talk about how this controversial technology might affect your shopping list for next year; but first a refresher on PCI.

If it’s unclear where PCI Express would be located, here are some directions. Starting from the CPU and continuing outward toward a NIC or a disk controller, you'll run into the I/O Bridge. There, just past the Memory Bridge, which we'll ignore for now, is a number of parallel connections from the I/O Bridge to each PCI slot in your machine. These PCI or PCI-X (PCI extended) links are what PCI Express will eventually replace.

In essence, PCI Express aims to trade those hard-to-implement parallel connections (PCI or PCI-X) with thinner, serial links that offer the combined advantage of faster performance and simplified manufacturing.

Despite an overlap with PCI-X, a bus interface that offers bandwidth in the range of 1GB to 4GB per second (yes, gigabytes), PCI Express is expected to go from initial speeds of 500MB per second up to a staggering 16GB per second.

Something is needed to replace PCI or PCI-X, but not all vendors agree that PCI Express is that replacement. In fact, other interconnect technologies such as HyperTransport, InfiniBand, Rapid I/O, and even PCI-X remain possible alternatives to Intel-backed PCI Express.

One advantage of PCI Express is that it has a variety of applications on servers, desktops, and laptops, which makes for a diversified theater of war where some localized battles can be easier to win than others.

Ironically, one of the first victories for the new technology will be to replace Intel's very own AGP (Accelerated Graphic Port) — an eyesore in many desktop motherboards that was developed to overcome the bandwidth limitations of PCI for data-intensive graphic applications.

It is also interesting to note that PCI Express will have an easy time getting into laptops thanks to the smaller ExpressCard form factor. Half the size of standard PC cards, ExpressCard is expected to begin shipping in 2004.

Gaining consensus in those cost-conscious platforms is fairly easy, but for Intel to win the interconnect battle in the server arena, it will need support form a variety of partners, including storage vendors. 

Naturally, the company is promoting a variety of facilitators to develop PCI Express-based cards, including a development kit and an interoperability lab for testing solutions. Adaptec, which introduced an Ultra320 SCSI RAID card based on PCI Express during IDF, is testing the PCI Express waters. It's reasonable to expect other vendors to embrace Intel solutions.

Stay tuned as we move into 2004: The war is just beginning.