Is System I/O in AS/400's Future?

To many industry observers the formation of the Future I/O and Next Generation I/O groups--two separate and distinct organizations each self-chartered with designing the I/O specification of the future--held ominous overtones. Many ISVs and hardware manufacturers wavered between sitting on their hands and waiting for a victor to emerge, and ramping up their resources to support two clashing specifications in parallel. Analysts and vendors alike hoped the two groups would come to their senses and work together to create one unifying I/O spec.

Well, the hoped-for has happened with the recent merger announcement of the two organizations and the soon-to-be-jointly-created System I/O specification.

As reported in myriad industry publications over the past year, advancements in distributed computing and "e-everything" have emphasized the shortcoming of PCI and the evolutionary PCI-X specifications. Many industry heavyweights--IBM, Hewlett Packard, Intel, Compaq and Sun included--determined that a channel-based, switched-fabric I/O architecture would not only eliminate those PCI failings, but would lay the groundwork for revolutionary I/O processes well into future hardware generations.

While PCI has been supported in some fashion on the AS/400 platform since 1996, IBM this past August announced an I/O expansion tower that spreads PCI support across the product line. "That brings PCI from the bottom to the top of our high end systems," says Bruce Walk, AS/400 chief engineering manager for I/O infrastructure. And IBM's AS/400 planners plan to stay the course on the PCI roadmap.

Walk says that while there's no specific time frame to be announced, AS/400 designers see no reason to deviate from the PCI-to-PCI-X-to-System I/O evolutionary process most of the industry is likely to follow. "Our customers want to be comfortable with the technology. AS/400 users don't tend to be technical advocates who need to be bleeding edge. So our intent is to leverage the benefits of PCI and PCI-X."

System I/O expects to provide a range of performance for entry-level through high-end data-center class servers using interoperable links with aggregate bandwidths of 500MB/second, 2GB/second, and 6GB/second and a 2.5Gb/second "wire" signaling rate. The specification will eventually replace shared bus I/O. The current standard, PCI, offers a bandwidth of 500MB/second and its next generation PCI-X expects to bump that to 1GB/second using the same form factor. But that's as high as engineers think they can go with its bus-based architecture that forces all I/O processes to share the same bus.

"The two groups are putting their heads together and defining that [System I/O] standard," says Walk, adding that there are several AS/400 engineers involved in the process. "And there are lots of benefits in time to market by following industry standards." He adds a warning, however, "Industry groups can get sidetracked, and we could go in a different direction if it's best for our customers."

Walk emphasizes that, regardless of what specs are in the offing, in designing an appropriate system configuration, it's still important to approach each customer's needs individually. "We ask what are you really trying to do with the system. What we've found is that at the system level and with LAN and DASD performance, [PCI] maps very well to most customers needs."

Estimating that version 1.0 of the combined spec will be ready by year-end 1999, the System I/O group is planning a fourth quarter participant event to update the industry and solicit involvement in the new specification's development. Initial products are expected in 2001.

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