SAN MATEO, Calif. No one wants to call it a bus war, but PC server makers are digging in over their choice of I/O.
In a press announcement planned for Monday, March 17, Fujitsu-Siemens, Hewlett-Packard and IBM will come out publicly supporting PCI-X 2.0 as the next-generation slot for their systems through 2005. Representatives from the group, which accounts for more than half the PC servers sold worldwide, suggest they are likely to switch to PCI Express slots starting in late 2005.
On the other side of the fence, Dell Computer is sticking to plans it tipped last year at a closed-door meeting of key suppliers to be among the first to ship systems including servers with PCI Express. "We have done the analysis and have come to the conclusion that Express is the route we want to go, and our customers and suppliers are in support of our plans," said a Dell spokeswoman.
PC makers on both sides of the line said they will use PCI Express in desktops and notebooks, but the more conservative server market is where the debate has become heated.
PCI-X is an extension of the parallel PCI bus that will run in version 2.0 at speeds of 266 and 533 MHz. Express, formerly 3GIO, is a serial interconnect developed by Intel Corp. and others that will first be used in 2004-class systems running at speeds of 2.5 Gbits/second per channel.
The three big server makers are coalescing around the idea of switching to PCI Express probably in late 2005. That's when both a hot pluggable module and a 5-6.5 Gbit/second signaling scheme for Express is expected to emerge. Users will be best served by making the I/O transition at that time, when Express has more apparent user advantages and is more mature, the server makers said.
"In the technology business it's all about timing. We think PCI-X 1.0 and 2.0 are the preferred slots through 2005. In 2006, there's a good chance things will shift [to Express] if Intel stays the course," said Kimball Brown, business development manager for ServerWorks (Santa Clara, Calif.), which is issuing the PCI-X announcement next week.
S. Bala Cadambi, PCI Express initiative manager for Intel, said the decision by the server makers would not disrupt his overall efforts. "We see the transition coming in 2004, as we have said. Our work on a generation two is for 2006 and requirements for it are just starting to be developed," he said.
ServerWorks, a Broadcom division that makes server chip sets, will not support PCI Express directly in its chip sets until after the 533 MHz PCI-X generation, although it does sit on committees defining the Express specification. That decision may cost the company some design wins at Dell where it currently claims sockets in seven of the company's eight PC servers.
"We are not convinced Dell is going 100 percent to Intel. They have a dual-source strategy that allows them to beat competitors up over price," said Brown.
Even PCI-X supporters may use Intel chip sets with PCI Express in some servers although they will not use Express for slots in those systems.
"Express may be interesting for a chip-to-chip connection in its first generation. Over time you'll see a strategy that supports both interconnects," said Karl Walker, chief technology officer for PC server hardware at HP.
IBM has not undecided whether it will use Intel chip sets with Express in some of its servers, but it will not provide Express slots through 2005, said Tom Bradicich, chief technology officer for IBM's PC server group.
ServerWorks claims sockets in most HP PC servers and all but some high-end four-way IBM servers. It also claims it supplies chip sets for all Fujitsu-Siemens and NEC PC servers.
Intel jumped back into the market for server chip sets last year. It claims its PCI Express chip sets probably emerging late this year will offer faster, lower latency connections than PCI-X parts and require fewer chips, saving OEMs money and board space.
Plans at HP, IBM and elsewhere to shift to Expr ess after the 533 MHz version of PCI-X means work announced last year on a 1066MHz version of PCI-X is not likely to bear fruit.
"There's some research going on in 1066 PCI-X but there's not commitment," said Walker.
"There's some evaluation going on by our engineers. You have to evaluate the last version you do not use," added Bradicich.
The PCI-X/Express split is forcing chip and adapter card makers to develop products for both PCI-X and Express, an R&D burden most companies would like to forgo in a down year. In the graphics field, chip makers are being driven by Intel to deliver accelerators with Express late this year, hard on the heels of getting out their first chips with the fast and complex AGP 8x interface.
"We will see a spike in R&D at the prototyping level," due to the back-to-back emergence of AGP 8x and Express, said David Orton, president of ATI Technologies Inc. (Markham, Ontario), a leading graphics chip company.
To mitigate the difficulties somewhat, Intel and Se rverWorks could both supply bridge chips to the other interface. Intel is expected to produce Express-to-PCI-X bridges after a standard for the devices is finished. ServerWorks said it does not have plans for such chips in the next 12 months.