PCI-X Spec Gets Warm Reception

Welcome Guest. | Log In| Register | Membership Benefits

September 17, 1998 (12:15 PM EDT)

By Andy Patrizio,

The new Peripheral Component Interconnect bus architecture, called PCI-X, could be in Intel-based servers by the end of 1999 if everything goes well with the PCI Steering Committee, a standards body.

PCI-X was developed by IBM, Hewlett-Packard, and Compaq, normally competitors in the PC server market, to provide a faster channel for high-speed input/output devices like gigabit Ethernet cards and Fibre Channel. The trio turned the specification over to the PCI Steering Committee for review, and so far, the committee likes what it sees.

"It looks very good, very well thought through," said Warren Questo, chairman of the committee. "We are very grateful that they are bringing this to the PCI standards body to make it open to the entire industry."

Intel (company profile), which developed the PCI spec, is a part of the committee and is also evaluating PCI-X. Although the chip giant isn't opposed to PCI-X, Intel doesn't see it as a pressing concern.

"We think there is more than adequate bandwidth coverage on the existing PCI bus," said Mitch Schults, director of server I/O marketing at Intel. Intel's biggest concern is the complexity of the new bus could cause compatibility problems, said Schults.

Compaq, IBM, and HP want a high-speed bus for servers without creating a bus war and won't gain financially if the PCI-X is adopted, said Carl Walker, vice president of technology development for the enterprise computing group at Compaq.

PCI-X not only increases the speed of the PCI bus but also the number of high-speed slots. With the current design, PCI slots run at 33 MHz and one slot can run at 66 MHz. With PCI-X, one slot can run at 133 MHz, double the current top speed, and the rest can run at 66 MHz or 100 MHz for a collective throughput of 1 gigabit per second. Walker doubts PCI-X will make its way into desktop computers because the increased speed comes at additional cost.

PCI-X is fully backward compatible with standard PCI, which is necessary for acceptance. "That was the prime directive: to add new capabilities but not break anything in the process," said Walker.

The steering committee will be checking the spec closely for that. "We need to make sure legacy things are maintained," said Questo. "We want to make sure it meets the needs, and the implementation doesn't add undue complexity or add costs or leave holes in the spec."

Adding this kind of speed requires a lot of reworking the electronics and design, which could break compatibility in some instances.

If all goes well, the committee could approve the PCI-X spec within six months and servers with the new I/O could appear by the end of 1999, said Questo. He's optimistic because, so far, there has been no objection from Intel, original equipment manufacturers, or peripheral card vendors.

Intel is more concerned about improving the reliability of PCI's shared bus, something hardware vendors and peripheral-card makers have complained about. If one slot goes down it can take several cards with it.

"So [PCI-X] is interesting and it's an improvement, but it doesn't fundamentally get at the core of where we think I/O needs to go," said Schults.