Switch Fabrics Get Scalable

PCI Express Is Ubiquitous
No surprise here—PCI Express is a rousing success. It's the interface of choice on microcontrollers and processor support chip sets. PCI Express is being used for board and chassis interconnects, but continues as a host-based solution. Or is it?

Advanced Switching, the PCI Express fabric, seems to have lost out to the other fabrics and PCI Express virtualization. PCI Express virtualization will be the hot ticket this year. Nonetheless, this will be a year for building and experimentation on the virtualization side.

PCI Express adoption will continue to be pushed because of performance requirements in new systems. It will be found on all board and mezzanine form factors, from the compact EPIC Express to the large AdvancedTCA racks.

HyperTransport Moving Off- Board
HyperTransport is more of an on-board chip-to-chip interconnect made famous by companies like AMD and Broadcom with their high-performance, multichip systems. HTX (HyperTransport Expansion) is the standard for moving HyperTransport offboard.

The reasoning behind HTX is the same as PCI Express—getting high-speed access to peripherals without going through an additional level of translation. Look for HTX boards like QLogic’s InfiniPath to be more common as the HTX connector shows up on more boards and high-performance interfaces such as InfiniBand become add-ons.

Changing The Software
The biggest change this year will come on the software side with the installation of more fabric hardware. Hardware adoption will continue to proceed, quickly running existing applications. But reprogramming will provide even better throughput and more functionality. Protocols like iSCSI and features like RDMA require application and operating-system modification. The software to handle this is now available and well understood. And, conventional buses aren’t going away, but fabrics will ultimately dominate.

See Figure 4